Recent theoretical studies have suggested that Kitaev physics and such effects as formation of a mysterious spin-liquid state can be expected not only in $\alpha \text{−}{\mathrm{RuCl}}_3$ and iridates, but also in conventional $3d$ transition metal compounds. Using dc and ac magnetometry, thermodynamic, and ${}^{23}\mathrm{Na}$ nuclear magnetic resonance (NMR) measurements we studied such a candidate material ${\mathrm{Na}}_3{\mathrm{Co}}_2{\mathrm{SbO}}_6$. A full phase diagram of ${\mathrm{Na}}_3{\mathrm{Co}}_2{\mathrm{SbO}}_6$ in a wide range of magnetic fields and temperatures is presented. The results demonstrate transformation of the antiferromagnetic structure under the external magnetic field, gradual development of the saturation phase, as well as evidence of gapped behavior in certain parts of the phase diagram.

Ferromagnetic Heusler alloys exhibiting martensitic transformations are known to change their shape in an external magnetic field. Magnetization, electric resistance, and specific heat as a function of temperature are examined in ${\mathrm{Ni}}_{54}{\mathrm{Fe}}_{19}{\mathrm{Ga}}_{27}$ single crystal. Structural transition appears as sharp anomaly in these dependencies. This points to an avalanchelike character of martensitic transformation. The jump in resistivity at the structural phase transition and the lower density of states at the Fermi level in the martensite phase supports the hypothesis of the Jahn-Teller origin of the martensitic transformation. Magnetic measurements show that transformation to the martensitic phase is accompanied by the increase of spontaneous magnetization and an increase of magnetocrystalline anisotropy. Magnetization increase is due to different Curie temperatures of austenite and martensite. These were determined from critical behavior using Arrott plot. Additional analysis of magnetic behavior indicates ferrimagnetic ordering in this nonstoichiometric compound. Intrinsic properties of the compound are analyzed with respect to both of the actuation modes possible in magnetic shape-memory alloys. However, neither a magnetically induced martensite transformation nor a magnetically induced reorientation of variants has been observed.

In order to understand the electronic origin of the inverse magnetocaloric effect observed in a Ni–Co–Mn–In system we used a combination of indirect experimental probes as magnetization, resistivity and specific heat. The findings are compared with the band structure of isostructural Heusler alloys such as Ni–Mn–Ga. We suggest that the inverse magnetocaloric effect in Ni–Co–Mn–In originates from the high density of states close to Fermi energy. Within the austenite state this causes ferromagnetic band splitting. The structural change to the martensite allows an alternative way to reduce the high density of states at lower temperatures, which does not require band splitting and thus does not support ferromagnetic order.

The trigonal layered quaternary tellurate ${\mathrm{Na}}_2\mathrm{MnTe}{\mathrm{O}}_6$ has been studied by means of various techniques to clarify its magnetic properties. The crystal structure of this compound is based on the triangular arrangement of all cations in the parallel layers with the space group $P\overline{3}1c$. By using symmetry analysis of the magnetic neutron scattering data, we have found that the solution for the magnetic structure corresponds to the magnetic Shubnikov group $R{\overline{3}}^{\prime }{c}^{\prime }$ (No. 167.4.1337). ${\mathrm{Mn}}^{4+}$ ions in an octahedral environment form a triangular network where all spins are directed from the center of each triangle. Overall magnetic structure in ${\mathrm{Na}}_2\mathrm{MnTe}{\mathrm{O}}_6$ is commensurate $120{}^{\circ }$ spin helix with propagation vector $\mathit{k}=\left(1/3,1/3,1/3\right)$ in variance with planar spin structure in structurally equivalent ${\mathrm{Li}}_2\mathrm{MnTe}{\mathrm{O}}_6$ with magnetic propagation vector $\mathbf{k}=\left(1/3,1/3,0\right)$. The magnetization measurements show that ${\mathrm{Na}}_2\mathrm{MnTe}{\mathrm{O}}_6$ experiences an antiferromagnetic order at $T_{\mathrm{N}}=5.5\mathrm{K}$. NMR, electron spin resonance, and thermodynamics experiments demonstrate the extended temperature region of 2D short-range correlations well above the ordering temperature.

Antiferromagnetic PbMnTeO₆, also known as mineral kuranakhite, has been reported recently to have all three cations in trigonal prismatic coordination, which is extremely unusual for both Mn(4+) and Te(6+). In this work, the phase was reproduced with the same lattice parameters and Néel temperature T_N = 20 K. However, powder neutron diffraction unambiguously determined octahedral (trigonal antiprismatic) coordination for all cations within the chiral space group P312. The same symmetry was proposed for SrMnTeO₆ and PbGeTeO₆, instead of the reported space groups P2m and P31m, respectively. PbMnTeO₆ was found to be a robust antiferromagnet with an assumingly substantial scale of exchange interactions since the Néel temperature did not show any changes in external magnetic fields up to 7 T. The determined effective magnetic moment μ_eff = 3.78μ_B was in excellent agreement with the numerical estimation using the effective g-factor g = 1.95 directly measured here by electron spin resonance (ESR). Both specific heat and ESR data indicated the two-dimensional character of magnetism in the compound under study. The combination of chirality with magnetic order makes PbMnTeO₆ a promising material with possible multiferroic properties.