Controlling spin current polarization through non-collinear antiferromagnetism.

The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn3GaN, in which the triangular spin structure creates a low magnetic symmetry while maintaining a high crystalline symmetry. We demonstrate that epitaxial Mn3GaN/permalloy heterostructures can generate unconventional spin-orbit torques at room temperature corresponding to out-of-plane and Dresselhaus-like spin polarizations which are forbidden in any sample with two-fold rotational symmetry. Our results demonstrate an approach based on spin-structure design for controlling spin-orbit torque, enabling high-efficient antiferromagnetic spintronics.

Anisotropic spin-orbit torque generation in epitaxial SrIrO3 by symmetry design.

Spin-orbit coupling (SOC), the interaction between the electron spin and the orbital angular momentum, can unlock rich phenomena at interfaces, in particular interconverting spin and charge currents. Conventional heavy metals have been extensively explored due to their strong SOC of conduction electrons. However, spin-orbit effects in classes of materials such as epitaxial 5d-electron transition-metal complex oxides, which also host strong SOC, remain largely unreported. In addition to strong SOC, these complex oxides can also provide the additional tuning knob of epitaxy to control the electronic structure and the engineering of spin-to-charge conversion by crystalline symmetry. Here, we demonstrate room-temperature generation of spin-orbit torque on a ferromagnet with extremely high efficiency via the spin-Hall effect in epitaxial metastable perovskite SrIrO3 We first predict a large intrinsic spin-Hall conductivity in orthorhombic bulk SrIrO3 arising from the Berry curvature in the electronic band structure. By manipulating the intricate interplay between SOC and crystalline symmetry, we control the spin-Hall torque ratio by engineering the tilt of the corner-sharing oxygen octahedra in perovskite SrIrO3 through epitaxial strain. This allows the presence of an anisotropic spin-Hall effect due to a characteristic structural anisotropy in SrIrO3 with orthorhombic symmetry. Our experimental findings demonstrate the heteroepitaxial symmetry design approach to engineer spin-orbit effects. We therefore anticipate that these epitaxial 5d transition-metal oxide thin films can be an ideal building block for low-power spintronics.

Influence of dairy by-product waste milk on the microbiomes of different gastrointestinal tract components in pre-weaned dairy calves.

The community structure of colonised bacteria in the gastrointestinal tracts (GITs) of pre-weaned calves is affected by extrinsic factors, such as the genetics and diet of the calves; however, the dietary impact is not fully understood and warrants further research. Our study revealed that a total of 6, 5, 2 and 10 bacterial genera showed biologically significant differences in the GITs of pre-weaned calves fed four waste-milk diets: acidified waste milk, pasteurised waste milk, untreated bulk milk, and untreated waste milk, respectively. Specifically, generic biomarkers were observed in the rumen (e.g., Bifidobacterium, Parabacteroides, Fibrobacter, Clostridium, etc.), caecum (e.g., Faecalibacterium, Oxalobacter, Odoribacter, etc.) and colon (e.g., Megamonas, Comamonas, Stenotrophomonas, etc.) but not in the faeces. In addition, the predicted metabolic pathways showed that the expression of genes related to metabolic diseases was increased in the calves fed untreated waste milk, which indicated that untreated waste milk is not a suitable liquid diet for pre-weaned calves. This is the first study to demonstrate how different types of waste milk fed to pre-weaned calves affect the community structure of colonised bacteria, and the results may provide insights for the intentional adjustment of diets and gastrointestinal bacterial communities.

Effects of stocking density on behavior, productivity, and comfort indices of lactating dairy cows.

The objective of this study was to investigate the effects of different stocking densities of 82 (0.82 cows per freestall and feed bin), 100, and 129% on behavior, productivity, and comfort indices of lactating Holstein dairy cows. Twenty-seven lactating cows (15 primiparous and 12 multiparous) were assigned to 1 of the 3 treatments, which were balanced for parity, milk yield, days in milk, and body weight in a 3×3 Latin square design with 14-d periods. After 7 d of adaptation to the treatments, lying time and bouts were recorded at 1-min intervals for 3 d, DMI and feeding time were monitored electronically by feed bins, and rumination time was quantified at 2-h periods for 5 d during each period. The cow comfort index, stall standing index, stall perching index, and stall use index (SUI) were calculated using 10-min scan samples of video recording from d 8 to 10 of each period. Milk yield was recorded from d 8 to 12 and milk composition was determined from composite samples on d 12 in each period. Daily lying time, lying bouts, and bout duration did not differ among the stocking densities. The ratio of lying time ≥12 h/d (the number of cows with daily lying time ≥12 h/d divided by number of cows per pen) was higher for cows housed at 82% stocking density compared with those housed at 100% stocking density, with stocking density of 129% intermediate. Hourly lying time was lower at 100% stocking density compared with 82 and 129% stocking densities during the peak period (2300-0400 h), determined based on diurnal pattern of lying time. Daily dry matter intake, feeding time, and feeding rate were not affected by stocking density. After morning milking, dry matter intake and feeding time was reduced at 129 versus 82% stocking density during peak feeding time (0600-0800 h), determined based on diurnal patterns of feeding behavior. Stocking density had no effect on rumination time, milk yield and milk composition. The ratio of SUI ≥85% (mean of the number of SUI ≥85% divided by the number of SUI at 10-min scan samples during a 24-h period) was lower at 129 versus 82% stocking density, with stocking density of 100% intermediate. During peak lying time after evening milking (2300-0400 h), both cow comfort index and SUI were higher at 129 than at 100% stocking density. The SUI was lower 2h after morning milking (0800-0900 h) for cows housed at 129% compared with those housed at 82 and 100% stocking densities. In conclusion, when compared with 100% stocking density, understocking contributed to natural behaviors of cows that including lying, feeding, and rumination behavior, whereas overstocking did not cause negative effect on behavior, productivity, and comfort indices of cows in this study.

Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi3 (A = Sr and Ba).

Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.