Evidence of Long-Range and Short-Range Magnetic Ordering in the Honeycomb Na3Mn2SbO6 Oxide.

We present a comprehensive study of the synthesis, structure, and magnetic properties of the honeycomb oxide Na3Mn2SbO6 supported by neutron diffraction, heat capacity, and magnetization measurements. The refinements of the neutron diffraction patterns (150, 50, and 45 K) using the Rietveld method confirm the monoclinic (S. G. C2/m) structure. Temperature-dependent magnetic susceptibilities measured at varying fields along with the heat capacity measurements demonstrate the coexistence of long-range ordering (∼42 K) and short-range ordering (∼65 K). The field-dependent isothermal magnetization measurements at 5 K indicate a spin-flop transition around 5 T. Rietveld refinements of the low-temperature (below 45 K) neutron diffraction data further confirm the long-range magnetic ordering. In addition, the temperature variation of the lattice parameters obtained from the neutron powder diffraction analysis exhibited a distinct anomaly near the antiferromagnetic transition temperature. The appearance of the concomitant broadened backgrounds in the neutron powder diffraction data collected at 80, 50, and 45 K supports the short-range ordering. The resultant magnetic structure consists of spins that are aligned antiparallel with the nearest neighbors and also with the spins of the adjacent honeycomb layers. The occurrence of a fully ordered magnetic ground state (Neel antiferromagnetic (AFM)) in Na3Mn2SbO6 consolidates the significance of fabricating new honeycomb oxides.

The neoadjuvant rectal score and a novel magnetic resonance imaging based neoadjuvant rectal score are stage independent predictors of long-term outcome in locally advanced rectal cancer.

AIM: Neoadjuvant rectal (NAR) score is an early surrogate for longer-term outcomes in rectal cancer undergoing radiotherapy and resection. In an era of increasing organ preservation, resection specimens are not always available to calculate the NAR score. Post-treatment magnetic resonance imaging (MRI) re-staging of regression is subjective, limiting reproducibility. We explored the potential for a novel MRI-based NAR score (mrNAR) adapted from the NAR formula. METHODS: Locally advanced rectal cancer patients undergoing neoadjuvant therapy (nCRT) and surgery were retrospectively identified between 2008 and 2020 in a single cancer network. mrNAR was calculated by adapting the NAR formula, replacing pathological (p) stages with post-nCRT MR stages (ymr). Cox regression assessed relationships between clinicopathological characteristics, NAR and mrNAR with overall survival (OS) and recurrence-free survival (RFS). RESULTS: In total, 381 NAR and 177 mrNAR scores were calculated. On univariate analysis NAR related to OS (hazard ratio [HR] 2.05, 95% confidence interval [CI] 1.33-3.14, p = 0.001) and RFS (HR 2.52, 95% CI 1.77-3.59, p = 0.001). NAR 3-year OS <8 was 95.3%, 8-16 was 88.6% and >16 was 80%. mrNAR related to OS (HR 2.96, 95% CI 1.38-6.34, p = 0.005) and RFS (HR 2.99, 95% CI 1.49-6.00, p = 0.002). 3-year OS for mrNAR <8 was 96.2%, 8-16 was 92.4% and >16 was 78%. On multivariate analysis, mrNAR was a stage-independent predictor of OS and RFS. mrNAR corresponded to NAR score category in only 15% (positive predictive value 0.23) and 47.5% (positive predictive value 0.48) of cases for categories <8 and >16, respectively. CONCLUSIONS: Neoadjuvant rectal score is validated as a surrogate end-point for long-term outcomes. mrNAR categories do not correlate with NAR but have stage-independent prognostic value. mrNAR may represent a novel surrogate end-point for future neoadjuvant treatments that focus on organ preservation.

Carbon starvation of Pseudomonas aeruginosa biofilms selects for dispersal insensitive mutants.

BACKGROUND: Biofilms disperse in response to specific environmental cues, such as reduced oxygen concentration, changes in nutrient concentration and exposure to nitric oxide. Interestingly, biofilms do not completely disperse under these conditions, which is generally attributed to physiological heterogeneity of the biofilm. However, our results suggest that genetic heterogeneity also plays an important role in the non-dispersing population of P. aeruginosa in biofilms after nutrient starvation. RESULTS: In this study, 12.2% of the biofilm failed to disperse after 4 d of continuous starvation-induced dispersal. Cells were recovered from the dispersal phase as well as the remaining biofilm. For 96 h starved biofilms, rugose small colony variants (RSCV) were found to be present in the biofilm, but were not observed in the dispersal effluent. In contrast, wild type and small colony variants (SCV) were found in high numbers in the dispersal phase. Genome sequencing of these variants showed that most had single nucleotide mutations in genes associated with biofilm formation, e.g. in wspF, pilT, fha1 and aguR. Complementation of those mutations restored starvation-induced dispersal from the biofilms. Because c-di-GMP is linked to biofilm formation and dispersal, we introduced a c-di-GMP reporter into the wild-type P. aeruginosa and monitored green fluorescent protein (GFP) expression before and after starvation-induced dispersal. Post dispersal, the microcolonies were smaller and significantly brighter in GFP intensity, suggesting the relative concentration of c-di-GMP per cell within the microcolonies was also increased. Furthermore, only the RSCV showed increased c-di-GMP, while wild type and SCV were no different from the parental strain. CONCLUSIONS: This suggests that while starvation can induce dispersal from the biofilm, it also results in strong selection for mutants that overproduce c-di-GMP and that fail to disperse in response to the dispersal cue, starvation.

Magnetocaloric Effect in a Frustrated Gd-Garnet with No Long-Range Magnetic Order.

In this paper, the hyperkagome lattice of Gd spins in a garnet compound, Gd3CrGa4O12, is studied using bulk measurements and density functional computations, and the observation of large magnetocaloric effect corresponding to an entropy change, ΔSm = 45 J kg-1K-1 (≈ 45 J mol-1K-1) at 2 K, 8 T is reported. Though the compound defies long-range magnetic order down to 0.4 K, a broad feature below 10 K is observed in the specific heat with two low temperature anomalies at T* ≈ 0.7 K and TS ≈ 2.45 K. The anomaly at T* is reminiscent of one in Gd3Ga5O12, where it is related to the development of a complex magnetic phase, whereas the TS-peak is accounted for by a multilevel Schottky-like model. The spin-lattice relaxation times studied by nuclear magnetic resonance experiments show that the relaxation is dominated by the magnetic fluctuations in Cr which has a longer relaxation time compared to that of the garnet, Lu3CrGa4O12 containing a nonmagnetic rare earth. Our first-principles density functional theory calculations agree well with the experimental results and support short-range magnetic order in the Gd-sublattice and antiferromagnetism in the Cr-sublattice. The importance of spin fluctuations and short-range order in the rare earth and transition metal lattices in garnets resulting in large magnetocaloric effect is brought out through this work.

Real Time, Spatial, and Temporal Mapping of the Distribution of c-di-GMP during Biofilm Development.

Bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a dynamic intracellular signaling molecule that plays a central role in the biofilm life cycle. Current methodologies for the quantification of c-di-GMP are typically based on chemical extraction, representing end point measurements. Chemical methodologies also fail to take into consideration the physiological heterogeneity of the biofilm and thus represent an average c-di-GMP concentration across the entire biofilm. To address these problems, a ratiometric, image-based quantification method has been developed based on expression of the green fluorescence protein (GFP) under the control of the c-di-GMP-responsive cdrA promoter (Rybtke, M. T., Borlee, B. R., Murakami, K., Irie, Y., Hentzer, M., Nielsen, T. E., Givskov, M., Parsek, M. R., and Tolker-Nielsen, T. (2012) Appl. Environ. Microbiol. 78, 5060-5069). The methodology uses the cyan fluorescent protein (CFP) as a biomass indicator and the GFP as a c-di-GMP reporter. Thus, the CFP/GFP ratio gives the effective c-di-GMP per biomass. A binary mask was applied to alleviate background fluorescence, and fluorescence was calibrated against known c-di-GMP concentrations. Using flow cells for biofilm formation, c-di-GMP showed a non-uniform distribution across the biofilm, with concentrated hot spots of c-di-GMP. Additionally, c-di-GMP was found to be localized at the outer boundary of mature colonies in contrast to a uniform distribution in early stage, small colonies. These data demonstrate the application of a method for the in situ, real time quantification of c-di-GMP and show that the amount of this biofilm-regulating second messenger was dynamic with time and colony size, reflecting the extent of biofilm heterogeneity in real time.

Single Crystals of Cubic Rare-Earth Pyrochlore Germanates: RE2Ge2O7 (RE = Yb and Lu) Grown by a High-Temperature Hydrothermal Technique.

Large single crystals of Yb2Ge2O7 in the cubic Fd3̅ m space group, are synthesized and characterized from a high-temperature hydrothermal method (650°C/200 MPa in 1 M KF). The cubic phase displays spin frustration and possibly nonclassical quantum-spin behavior at low temperature. This is the first report of single crystals of this important phase of size and quality suitable for single-crystal neutron diffraction.

Dielectric and Raman investigations of structural phase transitions in (C2H5NH3)2CdCl4.

Temperature-dependent Raman and dielectric measurements have been carried out on (C2H5NH3)2CdCl4 single crystals. Raman studies reveal the presence of two structural phase transitions below room temperature at 216 K and 114 K. The phase transitions are marked by anomalies in temperature dependence of wave-number and full width half maximum (FWHM) of several vibrational modes. The transitions are also accompanied by anomalies in dielectric measurements. Raman and dielectric data indicate that the transition at 216 K is order-disorder in nature and is driven by re-orientation of organic ions, while the transition at 114 K is due to coupling between the CdCl6 octahedron and the organic chain. Further high temperature dielectric measurements reveal the presence of one more structural phase transition around 473 K across which dispersion in dielectric parameters is observed. The activation energies and relaxation time obtained for high temperature dielectric phases are characteristic of combined reorientation motions of alkyl ammonium cations.

Resilience of the Aurivillius structure upon La and Cr doping in a Bi5Ti3FeO15 multiferroic.

Combining the experimental techniques of high-resolution X-ray diffraction, magnetometry, specific heat measurement, and X-ray photoelectron, Raman and dielectric spectroscopy techniques, we have studied the influence of La and Cr doping on the crystal structure and magnetism of the room temperature Aurivillius multiferroic Bi5Ti3FeO15 by investigating the physical properties of (Bi4La)Ti3FeO15 and Bi5Ti3 (Fe0.5Cr0.5)O15. The parent (Bi5Ti3FeO15) and the doped ((Bi4La)Ti3FeO15 and Bi5Ti3(Fe0.5Cr0.5)O15) compounds crystallize in the A21am space group, which is confirmed through our analysis of high-resolution synchrotron X-ray diffraction data obtained on phase-pure polycrystalline powders. We determined the oxidation states of the metal atoms in the studied compounds as Fe3+, Ti4+, Cr3+, and La3+ through the analysis of X-ray photoelectron spectroscopy data. The magnetic susceptibilities of the three compounds are marked by the absence of a long-range ordered ground state, but dominated by superparamagnetic clusters with dominant antiferromagnetic interactions. This signature of short-range magnetism is also seen in specific heat as a low temperature enhancement which is suppressed upon the application of external magnetic fields up to 8 T. Our dielectric spectroscopy experiments showed that the three studied compounds display similar features in the dielectric constant measured as a function of frequency. However, upon doping La at the Bi site, the width of the ferroelectric hysteresis loop increases for (Bi4La)Ti3FeO15 compared to that of the parent compound Bi5Ti3FeO15, and with Cr doping, Bi5Ti3(Fe0.5Cr0.5)O15 becomes a leaky dielectric. The resilience of the Aurivillius crystal structure towards doping of La at the Bi site and Cr at the Fe site is clearly seen in the bulk properties of magnetic susceptibility, specific heat and the average crystal structure. The relevance of changes in the local structure is evident from our Raman spectroscopy and X-ray pair distribution function studies.

Early outcomes after post-cardiotomy extracorporeal membrane oxygenation in paediatric patients: a contemporary, binational cohort study.

OBJECTIVES: The aim of this study was to assess the early outcomes and risk factors of paediatric patients requiring extracorporeal membrane oxygenation after cardiac surgery (post-cardiotomy). METHODS: Retrospective binational cohort study from the Australia and New Zealand Congenital Outcomes Registry for Surgery database. All patients younger than 18 years of age who underwent a paediatric cardiac surgical procedure from 1 January 2013 to 31 December 2021 and required post-cardiotomy extracorporeal membrane oxygenation (PC-ECMO) in the same hospital admission were included in the study. RESULTS: Of the 12 290 patients included in the study, 376 patients required post-cardiotomy ECMO (3%). Amongst these patients, hospital mortality was 35.6% and two-thirds of patients experienced a major complication. Hypoplastic left heart syndrome was the most common diagnosis (17%). The Norwood procedure and modified Blalock-Taussig shunts had the highest incidence of requiring PC-ECMO (odds ratio of 10 and 6.8 respectively). Predictors of hospital mortality after PC-ECMO included single-ventricle physiology, intracranial haemorrhage and chylothorax. CONCLUSIONS: In the current era, one-third of patients who required PC-ECMO after paediatric cardiac surgery in Australia and New Zealand did not survive to hospital discharge. The Norwood procedure and isolated modified Blalock-Taussig shunt had the highest incidence of requiring PC-ECMO. Patients undergoing the Norwood procedure had the highest mortality (48%). Two-thirds of patients on PC-ECMO developed a major complication.

Magnetic structures and excitations in sawtooth olivine chalcogenides Mn2SiX4 (X = S, Se).

The Mn lattice in olivine chalcogenide Mn2SiX4 (X = S, Se) compounds forms a sawtooth, which is of special interest in magnetism owing to the possibility of realizing flat bands in magnon spectra, a key component in magnonics. In this work, we investigate the Mn2SiX4 olivines using magnetic susceptibility, and X-ray and neutron diffraction. We have determined the average and local crystal structures of Mn2SiS4 and Mn2SiSe4 using synchrotron X-ray, neutron diffraction, and X-ray total scattering data followed by Rietveld and pair distribution function analyses. It is found from the pair distribution function analysis that the Mn triangle that constitutes the sawtooth is isosceles in Mn2SiS4 and Mn2SiSe4. The temperature evolution of magnetic susceptibility of Mn2SiS4 and Mn2SiSe4 shows anomalies below 83 K and 70 K, respectively, associated with magnetic ordering. From the neutron powder diffraction measurements the magnetic space groups of Mn2SiS4 and Mn2SiSe4 are found to be Pnma and Pnm'a', respectively. We find that the Mn spins adopt a ferromagnetic alignment on the sawtooth in both Mn2SiS4 and Mn2SiSe4 but along different crystallographic directions for the S and the Se compounds. From the temperature evolution of Mn magnetic moments obtained from refining neutron diffraction data, the transition temperatures are accurately determined as TN(S) = 83(2) K and TN(Se) = 70.0(5) K. Broad diffuse magnetic peaks are observed in both the compounds, and are prominently seen close to TN, suggesting the presence of a short-range magnetic order. The magnetic excitations studied using inelastic neutron scattering reveal a magnon excitation with an energy corresponding to approximately 4.5 meV in both S and Se compounds. Spin correlations are observed to persist up to 125 K much above the ordering temperature and we suggest the possibility of short-range spin correlations responsible for this.

Successful surgical repair of pulmonary dominant common arterial trunk without aortic arch obstruction in a neonate.

The pulmonary dominant variant of the common arterial trunk has always been reported to be associated with aortic coarctation, or interruption of the aortic arch, along with a duct-dependent systemic circulation. This mandates a complex surgical repair with attendant high surgical mortality. We report a 23-day-old baby with a pulmonary dominant trunk with mild aortic hypoplasia but with an arch free of coarctation or interruption, who underwent successful surgical repair. In the preoperative evaluation of a common arterial trunk, pulmonary dominance may not necessarily denote an adverse risk factor when the aorta is only mildly hypoplastic.

Magnetic structure, excitations and short-range order in honeycomb Na2Ni2TeO6.

Na2Ni2TeO6has a layered hexagonal structure with a honeycomb lattice constituted by Ni2+and a chiral charge distribution of Na+that resides between the Ni layers. In the present work, the antiferromagnetic (AFM) transition temperature of Na2Ni2TeO6is confirmed atTN≈ 27 K, and further, it is found to be robust up to 8 T magnetic field and 1.2 GPa external pressure; and, without any frequency-dependence. Slight deviations from nominal Na-content (up to 5%) does not seem to influence the magnetic transition temperature,TN. Isothermal magnetization curves remain almost linear up to 13 T. Our analysis of neutron diffraction data shows that the magnetic structure of Na2Ni2TeO6is faithfully described by a model consisting of two phases described by the commensurate wave vectorsk→c,0.500and0.500.5, with an additional short-range order component incorporated in to the latter phase. Consequently, a zig-zag long-range ordered magnetic phase of Ni2+results in the compound, mixed with a short-range ordered phase, which is supported by our specific heat data. Theoretical computations based on density functional theory predict predominantly in-plane magnetic exchange interactions that conform to aJ1-J2-J3model with a strongJ3term. The computationally predicted parameters lead to a reliable estimate forTNand the experimentally observed zig-zag magnetic structure. A spin wave excitation in Na2Ni2TeO6atE≈ 5 meV atT= 5 K is mapped out through inelastic neutron scattering experiments, which is reproduced by linear spin wave theory calculations using theJvalues from our computations. Our specific heat data and inelastic neutron scattering data strongly indicate the presence of short-range spin correlations, atT>TN, stemming from incipient AFM clusters.

Absence of long-range magnetic order in lithium-containing honeycombs in the Li-Cr-Sb(Te)-O phases.

Li3((LiCr)(Te/Sb))O6compounds where Cr atoms along with Li and Te or Sb are part of a honeycomb and are studied using magnetic susceptibility, specific heat, x-ray photoelectron spectroscopy and neutron diffraction. The oxides stoichiometries as determined from the neutron diffraction studies are Li4.47Cr0.53TeO6and Li3.88Cr1.12SbO6with a stable oxidation state of +3 for Cr. Both the compounds crystallize in space groupC2/mwith intermixing of cations at the 4gsites leaving the 2asites preferentially for Te or Sb. Again, the Li+ions alone predominantly occur in the interlayer sites. Both the compounds show a broad anomaly in specific heat at 8 K, which is robust against 8 T. A corresponding anomaly is absent in the magnetic susceptibility but recovers from its derivative, dχ(T)/dT. We ascertain the magnetic anomaly temperatures (Ta) of Li4.47Cr0.53TeO6and Li3.88Cr1.12SbO6as 5.9 K and 6.7 K respectively from specific heat. Although the physical properties indicated a low temperature anomaly, neutron diffraction data did not reveal a magnetic signal or a structural anomaly down to 1.5 K. This rules out a conventional long-range ordered magnetic ground state in either compounds. Combining the results from specific heat, neutron diffraction and electron paramagnetic resonance, we put forth a scenario of depleted honeycomb lattice of Cr3+with predominant short-range magnetic correlations as the magnetic ground states of the title compounds.

Histoplasma Pyomyositis in a Patient with Disseminated Histoplasmosis and Anti-Synthetase Syndrome: Case-Based Review of Literature.

BACKGROUND: Histoplasmosis is an endemic mycosis caused by Histoplasma Capsulatum, a thermally dimorphic fungus with mycelial and yeast forms. Muscle involvement is infrequent in Histoplasmosis. CASE: A 49-year-old lady presented with generalized myalgia and arthritis of two-year duration, which had responded partly to glucocorticoids. The lady reported to us two years into the illness with ulcerative eyelid lesions, worsening myalgia, and painful skin nodules. Eventually, it turned out that anti-synthetase syndrome was the primary diagnosis with Histoplasma infection in the muscles, subcutaneous tissue, and eye. We herewith present the course of her illness and a review of Histoplasmosis of the muscle in literature. CONCLUSION: The differential diagnosis of painful muscle weakness is broad. Histoplasma capsulatum infection should be considered in immunosuppressed myositis patient presenting with orbital ulcers, skin nodules and worsening muscle weakness.

Third Molar Angulation Changes in Class II Div I Malocclusion Subjects Treated with Extraction of Four Premolars: A Retrospective Study.

AIM: The aim of this study was to assess the changes in maxillary and mandibular third molar inclinations in individuals with class II div 1 malocclusion, before and after orthodontic treatment with extraction of all four first premolars. MATERIALS AND METHODS: This retrospective study consisted of the pretreatment and posttreatment records of 30 patients that were obtained from the archives of the department of orthodontics and dentofacial orthopedics in A B Shetty Memorial Institute of Dental Sciences. The maxillary third molar's relation to the palatal plane and the mandibular third molar's relation to the mandibular plane were measured. The paired t test was used to calculate pre- and posttreatment changes. A value of P < 0.05 was considered to be statistically significant. RESULTS: The maxillary third molars showed a mean correction of 6.15° (P < 0.001) and the mandibular third molars showed a mean correction of 5.10° (P < 0.001). CONCLUSION: Maxillary third molars showed more uprighting when compared to the mandibular third molars and that both maxillary and mandibular third molars showed an improvement in their angulations to their respective planes after extraction of the first premolars. However, the results of the study cannot be analyzed to state if the third molars do become fully functional.

Overweight, obesity and chronic kidney disease.

The sharp rise in the prevalence of chronic kidney disease (CKD) that parallels an increase in the prevalence of obesity in the recent years is a cause for great concern. CKD increases the rate of cardiovascular disease (CVD), development of end-stage renal disease, and leads to premature death. Although no direct causality link between obesity and CKD can yet be established, this appears highly likely. CKD should be regarded as a major complication of overweight and obesity, regardless of whether the association was independent or through the influence of diabetes, hypertension, CVD, metabolic syndrome and high fructose intake. We review the literature on the complex but positive association between obesity and CKD, the pathological effect of excess adiposity in kidney injury and the potential role of weight reduction therapy in reducing the burden of CKD.

Absence of a long-range ordered magnetic ground state in Pr3Rh4Sn13 studied through specific heat and inelastic neutron scattering.

Signatures of absence of a long-range ordered magnetic ground state down to 0.36 K are observed in magnetic susceptibility, specific heat, thermal/electrical transport and inelastic neutron scattering data of the quasi-skutterudite compound Pr3Rh4Sn13 which crystallizes in the Yb3Rh4Sn13-type structure with a cage-like network of Sn atoms. In this structure, Pr3+ occupies a lattice site with D 2d point symmetry having a ninefold degeneracy corresponding to J = 4. The magnetic susceptibility of Pr3Rh4Sn13 shows only a weak temperature dependence below 10 K; otherwise remaining paramagnetic-like in the range, 10 K-300 K. From the inelastic neutron scattering intensity of Pr3Rh4Sn13 recorded at different temperatures, we identify excitations at 4.5(7) K, 5.42(6) K, 10.77(5) K, 27.27(5) K, 192.28(4) K and 308.33(3) K through a careful peak analysis. However, no signatures of long-range magnetic order are observed in the neutron data down to 1.5 K, which is also confirmed by the specific heat data down to 0.36 K. A broad Schottky-like peak is recovered for the magnetic part of the specific heat, C 4f, which suggests the role of crystal electric fields of Pr3+ . A crystalline electric field model consisting of 7 levels was applied to C 4f which leads to the estimation of energy levels at 4.48(2) K, 6.94(4) K, 11.23(8) K, 27.01(5) K, 193.12(6) K and 367.30(2) K. The CEF energy levels estimated from the heat capacity analysis are in close agreement with the excitation energies seen in the neutron data. The Sommerfeld coefficient estimated from the analysis of magnetic specific heat is [Formula: see text] mJ K-2 mol-Pr which suggests the formation of heavy itinerant quasi-particles in Pr3Rh4Sn13. Combining inelastic neutron scattering results, analysis of the specific heat data down to 0.36 K, magnetic susceptibility and, electrical and thermal transport, we establish the absence of long-range ordered magnetic ground state in Pr3Rh4Sn13.

Magnetic structure and field-dependent magnetic phase diagram of Ni2In-type PrCuSi.

The magnetic structure of the ternary equiatomic intermetallic compound PrCuSi is investigated using neutron powder diffraction experiments in 0 T as well as in external magnetic fields up to 2 T. The PrCuSi compound crystallizes in the hexagonal Ni2In-type structure, in the space group P63/mmc. In this structure, cationic ordering of Cu and Si takes place. The antiferromagnetic phase transition in the Pr sublattice takes place at [Formula: see text] K in 0 T. Under an external magnetic field of 2 T, a field-induced ferromagnetic phase is observed. Magnetoelastic coupling is evidenced by an increase in the unit cell volume. Clear signatures of a mixed antiferromagnetic and ferromagnetic phase in weak, intermediate fields, 0.4-0.8 T, are obtained from the present study. Using the present set of experimental data, we construct the H - T phase diagram of PrCuSi.

Disordered ferromagnetism in Ho2NiMnO6 double perovskite.

Magnetic and dielectric properties of the double perovskite Ho2NiMnO6 are reported. The compound is synthesized by nitrate route and is found to crystallize in monoclinic P21/n space group. Lattice parameters obtained by refining powder x-ray diffraction data are; a = 5.218(2) Å, b = 5.543(2) Å, c = 7.480(3) Å and the monoclinic angle is [Formula: see text](4). A phase transition is observed at [Formula: see text] K in the temperature-dependent magnetization curve, M(T). The inverse magnetic susceptibility, (1/[Formula: see text]) fits reasonably well with modified Curie-Weiss law by incorporating the paramagnetic response of Ho3+. 1/[Formula: see text] manifests as an upward deviation from ideal Curie-Weiss behaviour well above the ferromagnetic transition. Signs of inherent Griffiths phase pertaining to the Ni/Mn subsystem are visible when one subtracts the Ho3+ paramagnetic contribution from total susceptibility and does the power-law analysis. The magnetic hysteresis at 2 K gives the maximum value of magnetization [Formula: see text] [Formula: see text]/f.u. at 50 kOe. Field-derivative of magnetization at 2 K shows discontinuities which indicates the existence of metamagnetic transitions in this compound. This needs to be probed further. Out of the two dielectric relaxations observed, the one at low temperature may be attributed to phononic frequencies and that at higher temperature may be due to Maxwell-Wagner relaxation. A correlation between magnetic and lattice degrees of freedom is plausible since the anomaly in dielectric constant coincides with T C.

Magnetic glass state and magnetoresistance in SrLaFeCoO6 double perovskite.

Unusual features in magnetization resembling the kinetic arrest of a magnetic glass state are observed in the La-doped double perovskite, SrLaFeCoO6. Neutron powder diffraction experiments confirm the presence of antisite disorder as well as a lack of long-range magnetic order down to 4 K in this double perovskite which displays spin glass-like features in dc and ac susceptibilities. Magnetic relaxation observed through cooling and heating under unequal fields (CHUF) point towards unusual domain dynamics which is supported by a broad memory effect. Among the two anomalies that are observed at [Formula: see text] 75 K and at [Formula: see text] 250 K in the magnetic measurements, the former is associated with a spin-freezing temperature below which the magnetic glass state is experimentally verified. The magnetometric experiments detailed in the paper bring out the non-equilibrium metastable magnetic states in this disordered magnetic system. The magnetic glass state described above manifests in the electrical resistivity [Formula: see text] through the formation of a 'hard gap' because of the spin-exchange energy following the formation of magnetic glass. It is observed that the combination of disorder and magnetic glass state leads to a large, negative magnetoresistance (MR) of ≈47[Formula: see text] at 5 K in 8 T.