SPIN ORIENTATION AND MAGNETIC PROPERTIES OF CA2FEALO5

The Mössbauer effect has been used to determine the spin directions and magnetic space group of Ca2FeAlO5. At 5°K the spins on both the octahedral and tetrahedral sublattices are directed along the crystallographic a axis following the convention c<a<b. This is consistent with the magnetic space group Ic′m′m′ for Ca 2FeAlO5. The sublattices are individually antiferromagnetically ordered. The crystal structures of Ca 2FeAlO5 and Ca2Fe2O5 are apparently closely related but at 5°K as well as at room temperature, the spins in Ca2Fe2O5 are along the c axis. The Néel temperature of Ca2FeAlO5 is 60°±15°C. The internal fields at 5°K observed at the octahedral and tetrahedral iron sites of Ca2FeAlO5 are 502±10 and 454±10 kOe, respectively. © 1968 The American Institute of Physics.