High pressure synthesis and magnetic properties of corundum-type Ga1-Al FeO3 (x = 0, 0.25, 0.5)

Abstract

The orthorhombic oxide GaFeO3 transforms to corundum structure whereas AlFeO3 decomposes to its constituent oxides under high pressure and high temperature. • Antiferromagnetic ordering temperature increases with x in Ga1-xAlxFeO3 (0 ≤ x ≥ 0.5). • Spin cluster glass is observed in all these compounds at low temperatures. - Abstract: Metastable phases of Ga1-xAlxFeO3 (x = 0, 0.25, 0.5) have been prepared under high pressure (4.5 GPa) and high temperature (1000 °C) using a cubic-anvil high pressure apparatus. X-ray diffraction studies show that application of pressure transforms the structure of these compounds from the polar Pna21 to the non-polar R ̅ 3 c phase. Intriguingly, the orthorhombic phase of the compound with x = 1.0, synthesized at ambient pressure decomposes into their constituent oxides, Al2O3 (R ̅ 3 c) and Fe2O3 (R ̅ 3 c) under the same conditions of pressure and temperature. Magnetization measurements reveal antiferromagnetic ordering with a weak ferromagnetism below TN ~ 450 K, 590 K and 650 K, respectively. All these oxides exhibit a spin glass behavior at low temperatures. Analysis of ac susceptibility measurements indicate the existence of a cluster spin glass phase below T* ~ 45, 40 and 43 K respectively for x = 0, 0.25, 0.5. Such a re-entrant spin glass behavior arises due to antiferromagnetic interactions among the disordered Fe3+ ions in the octahedral site of the corundum structure.