ABSTRACT
Quantum materials that feature magnetic long-range order often reveal complex phase diagrams when localized electrons become mobile. In many materials magnetism is rapidly suppressed as electronic charges dissolve into the conduction band. In materials where magnetism persists, it is unclear how the magnetic properties are affected. Here we study the evolution of the magnetic structure in Nd_{1-x}Ce_{x}CoIn_{5} from the localized to the highly itinerant limit. We observe two magnetic ground states inside a heavy-fermion phase that are detached from unconventional superconductivity. The presence of two different magnetic phases provides evidence that increasing charge delocalization affects the magnetic interactions via anisotropic band hybridization.
ABSTRACT
New hybrid compounds LnCoCl(deg)2 (deg = diethyleneglycolate; Ln = Nd, Sm, Eu, Gd and Ho) have been synthesized by mixing cobalt and rare earth cations in a boiling diethyleneglycol (degH2) medium. Their crystallographic structures have been ab initio solved from synchrotron powder diffraction data. They consist of edge sharing tetrameric sub-units [(Ln2Co2)(deg)4(Cl)2] forming 1D infinite chains along the c parameter of a monoclinic unit cell (SG = C2/c). The five- and seven-coordination of Co(2+) and Ln(3+) cations inferred from the crystallographic results is confirmed by UV-visible absorption and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In the LnCoCl(deg)2 (Ln = Nd, Sm, Eu, Gd, Ho) series, weak antiferromagnetic superexchange interactions have been evidenced, between high spin Co(2+) and Ln(3+) orbitally degenerate cations. These materials are considered as potential precursors for the simultaneous reduction of Co-Ln-glycolate species into bimetallic nanoparticles by the polyol process.
ABSTRACT
The vortex lattice (VL) in the mixed state of the stannide superconductor Yb3Rh4Sn13 has been studied using small-angle neutron scattering (SANS). The field dependences of the normalized longitudinal and transverse correlation lengths of the VL, ξ(L)/a0 and ξ(T)/a0, reveal two distinct anomalies that are associated with vortex-glass phases below µ0Hl ≈ 700 G and above µ0Hh â¼ 1.7 T (a0 is the intervortex distance). At high fields, around 1.7 T, the longitudinal correlation decreases abruptly with increasing fields indicating a weakening (but not a complete destruction) of the VL due to a phase transition into a glassy phase, below µ0Hc2 (1.8 K) ≈2.5 T. ξ(L)/a0 and ξ(T)/a0, gradually decrease for decreasing fields of strengths less than 1 T and tend towards zero. The shear elastic modulus c66 and the tilting elastic modulus c44 vanish at a critical field µ0Hl ≈ 700 G, providing evidence for a disorder-induced transition into a vortex-glass. A 'ring' of scattered intensity is observed for fields lower than 700 G, i.e. µ0Hc1 = 135 G < µ0H < 700 G. This low-field phenomenon is of different nature than the one observed at high fields, where ξ(L)/a0 but not ξ(T)/a0, decreases abruptly to an intermediate value.