V. A. Sarkisyan, I. A. Trojan, I. S. Lyubutin, A. G. Gavriliuk, A. F. Kashuba, “Magnetic collapse and the change of electronic structure of FeBO<nobr>$_3$</nobr> antiferromagnet under high pressure”, Pis'ma v Zh. Èksper. Teoret. Fiz., 2002, Volume 76, Issue 11,Pages <nobr>788

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Magnetic collapse and the change of electronic structure of FeBO$_3$ antiferromagnet under high pressure

V. A. Sarkisyan^a, I. A. Trojan^b, I. S. Lyubutin^a, A. G. Gavriliuk^b, A. F. Kashuba^a

^a Institute of Cristallography Russian Academy of Sciences, Moscow
^b Institute for High Pressure Physics, Russian Academy of Sciences

Abstract: The effect of high pressures up to 60 GPa on single-crystal and polycrystalline samples of iron borate $^{57}$FeBO$_3$ was studied by Mössbauer absorption spectroscopy ($^{57}$Fe nuclei) in a diamond anvil cell. Magnetic field $H_{\rm hf}$ at the$^{57}$Fe nuclei increases with pressure but abruptly drops to zero at $46\pm2\,$GPa, indicating the crystal transition from the antiferromagnetic to nonmagnetic state. This is accompanied by an abrupt change in the isomer shift and quadrupole splitting. Their values in the high-pressure phase are evidence for the transition of Fe$^{3+}$ ions from a high-spin ($S = 5/2$, $^6$А$_{1g}$) to low-spin ($S=1/2$, $^2$T$_{2g}$) state (spin crossover). This correlates with an abrupt decrease in the unit-cell volume (by $\sim9\%$) and optical gap. The change of the magnetic and electronic structures is explained by Mott's transition with rupturing of strong $d-d$-electron correlations.

PACS: 61.50.Ks, 75.30.Et, 75.50.-y, 76.80.+y

Received: 25.10.2002