Аннотация:We report on the static and dynamic magnetic properties of quasi-two dimensional honeycomb oxides A3M2SbO6 (A = Li, Na), which can be potentially interesting for the application in electrochemical power devices. Both compounds order antiferromagnetically with the Néel temperature ~ 15 and 17 K respectively. At high temperatures, the magnetic susceptibility follows the Curie-Weiss law with positive values of Weiss temperature ~ 8 K for Li sample and ~12 K for Na sample indicating predominance of ferromagnetic interactions. The effective magnetic moment is 4.3 B/f.u. and agrees satisfactorily with theoretical estimations using determined in our work effective g-value ~2.15 and assuming high-spin state of Ni2+.
Summarizing the data, the magnetic phase diagram for A3Ni2SbO6 were suggested (Fig. 1). With increasing magnetic field the TN phase transition boundary shifts slowly to lower temperature side. In additional, the field-induced spin-reorientation (spin-flop) phase is likely to be realized at low temperatures. The main superexchange interaction via half-occupied Ni eg (dz2, dx2-y2) orbitals is appears to be ferromagnetic. This assumption is in accordance with predominance of ferromagnetic coupling at high temperatures. At the same time, the observation of long range antiferromagnetic order implies antiferromagnetic interactions between the ferromagnetic layers providing the antiferromagnetic ground state of this compound.