CONDENSED MATTER
Magnetic properties of $\mathrm{FeB}_4\mathrm{O}_7$ and $\mathrm{MnB}_4\mathrm{O}_7$ tetraborates in three structure types
A. S. Shinkorenko Kirensky Institute of Physics, Federal Research Center KSC, Siberian Branch, Russian Academy of Sciences,
Krasnoyarsk, 660036 Russia
Abstract:
The crystal structure and magnetic properties of
$\mathrm{FeB}_4\mathrm{O}_7$ and
$\mathrm{MnB}_4\mathrm{O}_7$ tetraborates have been studied within DFT-GGA. The tetraborates can be found in several possible structural modifications. Three of them, namely,
$Pbca$ (
$\alpha$-
$\mathrm{ZnB_4O_7}$),
$Cmcm$ (
$\beta$-
$\mathrm{ZnB_4O_7}$ structure type), and
$P6_522$ (
$\gamma$-
$\mathrm{NiB_4O_7}$ structure type) have been considered here. The possible magnetic orderings in three structure types are described within group-theoretical analysis. The following DFT calculations allow finding the lowest energy magnetic structure for
$\mathrm{FeB}_4\mathrm{O}_7$ and
$\mathrm{MnB}_4\mathrm{O}_7$ in three structure types. The total energies of tetraborates in three structure types have been compared with and without taking into account the spin polarization. It has been found that
$\mathrm{MnB}_4\mathrm{O}_7$ and
$\mathrm{FeB}_4\mathrm{O}_7$ in the non-spin-polarized case have the
$\alpha$-
$\mathrm{ZnB_4O_7}$ and
$\gamma$-
$\mathrm{NiB_4O_7}$ structure types as the lowest energy structure, respectively. However, when the magnetic structure is taken into account, the antiferromagnetic
$\alpha$-
$\mathrm{ZnB_4O_7}$ phase becomes the ground state for both tetraborates. The pressure dependence of the enthalpy of
$\mathrm{FeB}_4\mathrm{O}_7$ and
$\mathrm{MnB}_4\mathrm{O}_7$ tetraborates has been studied. It has been found that the applied pressure results in the appearance of the
$\beta$-
$\mathrm{ZnB_4O_7}$ structure type as the lowest energy structure under pressure.
Received: 19.07.2022
Revised: 12.08.2022
Accepted: 22.08.2022
DOI:
10.31857/S1234567822180069
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