Field-Induced Spin Reorientation in ErCrO3

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Abstract
A field‐induced spin reorientation has been observed in the weak ferromagnet, ErCrO3, at temperatures below the Néel point, TN=133.2°K. With a magnetic field, H, along the a axis of this orthorhombic compound, the spontaneous magnetization rotates from the c axis, at H=0, to the a axis, at H=Ht. The ``transition'' field, Ht, increases from zero at TN to 11 kOe at T=22°K. The temperature dependence is discussed in terms of a formula which gives the first‐order Er3+ contributions to Ht. Above 120°K, the data can be fitted to the curve Ht=a(1‐T/TN)1/2, with a=8.1±0.5 kOe. The canting angle for the Cr3+ sublattices and the effective field, Heff, on the Er3+ ions have been estimated from spontaneous‐magnetization data. These data were obtained by extrapolating from high magnetic fields to H=0 for both the c and a axes. A canting angle of 35 mrad gives reasonable agreement with both sets of data, but Heff reverses sign on reorientation of the spins. At low temperatures, Heff≈−10 kOe along the c axis.