Neutron Diffraction Study of the Magnetic Properties of Rare-Earth-Iron Perovskites

A neutron diffraction study was made of the magnetic properties of the rare-earth-iron perovskites, NdFeO/sub 3/, HoFeO/sub 3/, and ErFeO/sub 3/, at temperatures ranging from 955 to 1.25 deg K. The iron ions in each of these compounds undergo a transition to an antiferromagnetic configuration in which each moment has six oppositely directed moments at nearest neighbor distances. The Neel temperatures are 760, 700, and 620 deg K for the compounds of Nd, Ho, and Er, respectively. The moment directions in HoFeO/sub 3/ and ErFeO/sub 3/ are parallel and antiparallel to the orthorhombic STA100! direction at room temperature: at 43 deg K the moments are found to be in a (1-bar10) plane. In HoFeO/sub 3/ the iron-ion moments at 1.25 K are parallel to STA001!: in ErFeO/ sub 3/ at the same temperature they are parallel to STA110!. The magnitudes of the ordered iron moments at temperature saturation are 4.57, 4.60, and 4.62 Bohr magnetons in NdFeO/sub 3/, HoFeO/sub 3/, and ErFeO/sub 3/, respectively. In the liquid helium temperature range, magnetic ordering transitions of the rare-earth ions in HoFeO/sub 3/ (T/sub N = 6.5 deg K) and ErFeO/sub 3/ (T/sub N/ = 4.3 deg K) are observed. The Er/sup 3+/ ion moments form a nearly ideal antiferromagnetic configuration in which a chain of parallel moments is surrounded by four chains of oppositely directed moments at nearest neighbor distances. In this compound the Er/sup 3+/ ion moments are parallel and antiparallel to STA001! and at 1.25 deg K have a magnitude of 5.8 Bohr magnetons. In HoFeO/sub 3/ the ions are ordered in a distorted antiferrormagnetic configuration in which, at 1.25 deg K, each Ho/sup 3+/ moment with magnitude of 7.5 Bohr magnetons, makes an angle, in the (001) plane, of about 27 deg with the STA010! direction so as to produce a net ferromagnetic moment of 3.4 Bohr magnetons per HoFeO/sub 3/ molecule parallel to STA100!. (auth)