Effect of High Pressures on Exchange and Hyperfine Interactions
in Rare-Earth Orthoferrites

A. G. Gavrilyuk¹, G. N. Stepanov¹, I. S. Lyubutin^2, *, A. S. Stepin², I. A. Troyan¹,
V. A. Sidorov¹, B. Palosz³, S. Stel’makh³, and M. Winzenick⁴

¹Institute of High-Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow oblast, 142092 Russia

²Institute of Crystallography, Russian Academy of Sciences, Moscow, 117333 Russia

³High Pressure Research Center, Polish Academy of Sciences, Warsaw, Poland

⁴Univesität-G-H Paderborn, 33098 Paderborn, Germany

*e-mail: lyubutin@magnet.crystal.msk.su

Received July 26, 1999

Abstract—The effect of high pressures P on the Néel temperature T_N , the crystal lattice parameters, and the
magnitude of the hyperfine magnetic field H^Sn at a nucleus of a diamagnetic tin atom was studied in pure and
tin-doped orthoferrites RFeO₃ (R = Nd, Lu). The dependence of these quantities on the geometry of the
exchange bonds, specifically, the angle and length of the chemical bond Fe–O–Fe(Sn), was analyzed. It was
established that under pressure the angular contribution decreases and the radial contribution increases T_N and
H^Sn, the radial contribution being greater than the angular contribution in absolute magnitude. Numerical esti-
mates were obtained for the angular and radial contributions to T_N and H^Sn. In lutecium orthoferrite, at P > 30 GPa
anomalies indicating a possible phase transition were observed in the behavior of the lattice parameters and the
value of H^Sn. © 2000 MAIK “Nauka/Interperiodica”.

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