We report the results of the experimental and theoretical study of the magnetic anisotropy of single crystals of the Co-doped lithium nitride Li 2 (Li 1−x Co x )N with x = 0.005, 0.01, and 0.02. It was shown recently that doping of the Li 3 N crystalline matrix with 3d transition metal (TM) ions yields superior magnetic properties comparable with the strongly anisotropic single-molecule magnetism of rare-earth complexes. Our combined electron spin resonance (ESR) and THz spectroscopic investigations of Li 2 (Li 1−x Co x )N in a very broad frequency range up to 1.7 THz and in magnetic fields up to 16 T enable an accurate determination of the energies of the spin levels of the ground state multiplet S ̂= 1 of the paramagnetic Co(I) ion. In particular, we find a very large zero field splitting (ZFS) of almost 1 THz (∼4 meV or 33 cm −1 ) between the ground-state singlet and the first excited doublet state. On the computational side, ab initio many-body quantum chemistry calculations reveal a ZFS gap consistent with the experimental value. Such a large ZFS energy yields a very strong single-ion magnetic anisotropy of easy-plane type resembling that of rare-earth ions. Its microscopic origin is the unusual linear coordination of the Co(I) ions in Li 2 (Li 1−x Co x )N with two nitrogen ligands. Our calculations also evidence a strong 3d−4s hybridization of the electronic shells resulting in significant electron spin density at the 59 Co nuclei, which may be responsible for the experimentally observed extraordinary large hyperfine structure of the ESR signals. Altogether, our experimental spectroscopic and computational results enable comprehensive insights into the remarkable properties of the Li 2 [Li 1−x (TM) x ]N magnets on the microscopic level.
We present magnetization measurements carried out on polycrystalline and single-crystalline samples of α-Li 2 IrO 3 under hydrostatic pressures up to 2 GPa and establish the temperature-pressure phase diagram of this material. The Néel temperature (T N ) of α-Li 2 IrO 3 is slightly enhanced upon compression with dT N /d p = 1.5 K/GPa. Above 1.2 GPa, α-Li 2 IrO 3 undergoes a first-order phase transition toward a nonmagnetic dimerized phase, with no traces of the magnetic phase observed above 1.8 GPa at low temperatures. The critical pressure of the structural dimerization is strongly temperature dependent. This temperature dependence is well reproduced on the ab initio level by taking into account lower phonon entropy in the nonmagnetic phase. We further show that the initial increase in T N of the magnetic phase is due to a weakening of the Kitaev interaction K along with the enhancement of the Heisenberg term J and off-diagonal anisotropy . Our study reveals a common thread in the interplay of magnetism and dimerization in pressured Kitaev materials.
A new copper vanadyl arsenate, Cu(VO)2(AsO4)2, was synthesized via the chemical vapor transport
method.
Cu(VO)2(AsO4)2 adopts an original
structure type. It is characterized by layers formed by edge-sharing
and corner-sharing V-centered octahedra resulting in a unique topology
that was hitherto not reported for vanadates. Single CuO6 octahedra connect vanadate layers into a rigid framework. The thermal
expansion of the framework studied by the single-crystal HT X-ray
diffraction is reported. The magnetic behavior of Cu(VO)2(AsO4)2 shows an interplay of ferromagnetic
V4+–V4+ and antiferromagnetic Cu2+–V4+ interactions that result in a ferrimagnetic
long-range order below T
C = 66 K.
We explore the effect of heat treatment in argon atmosphere under various temperatures up to 500 • C on single crystals of α-RuCl3 by study of the mass loss, microprobe energy dispersive x-ray spectroscopy, powder x-ray diffraction, electrical resistance as well as low-temperature magnetic susceptibility and specific heat. Clear signatures of dechlorination and oxidation of Ru appear for annealing temperatures beyond 300 • C. Analysis of the specific heat below 2 K reveals a RuO2 mass fraction of order 1% for pristine α-RuCl3 which increases up to 20% after thermal annealing, fully consistent with mass-loss analysis. The small RuO2 inclusions drastically reduce the global electrical resistance and may thus significantly affect low-temperature thermal transport and Hall effect.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.