HIGH-PRESSURE MAGNETIC PROPERTIES AND P-T PHASE DIAGRAM OF IRON BORATE FeBO₃
Gavriliuk A.G., Trojan I.A., Lyubutin I.S., Sarkissian V.A., Ovchinnikov S.G.

Received: July 6, 2004

PACS: 71.27.+a, 61.50.Ks, 71.30.+h

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The high-pressure magnetic states of iron borate ⁵⁷FeBO₃ single crystal and powder samples have been investigated in diamond anvil cells by nuclear forward scattering (NFS) of synchrotron radiation at different temperatures. In the low-pressure (03+ ions from the high-spin 3d⁵ (S=5/2, ⁶A_1g) to the low-spin (S=1/2, ²T_2g) state (spin crossover) due to the insulator-semiconductor-type transition with extensive suppression of strong d-d electron correlations. At low temperatures, NFS spectra of the high-pressure phase indicate magnetic correlations in the low-spin system with the magnetic ordering temperature about 50 K. A tentative magnetic P-T phase diagram of FeBO₃ is proposed. An important feature of this diagram is the presence of two triple points where magnetic and paramagnetic phases of the high-spin and low-spin states coexist.