Synthesis, structure and exchange bias in Cr2O3/CrO2/Cr2O5 particles

Abstract We report on the synthesis, structure and magnetic properties of a novel exchange bias system with Cr 2 O 3 /CrO 2 /Cr 2 O 5 interfaces. Chromium oxide particles with mixed chromium valences were prepared by sintering CrO 3 in air. X-ray diffraction patterns show that CrO 3 lost its oxygen gradually with increasing temperature and time through Cr 3 O 8 , Cr 2 O 5 , CrO 2 , and finally Cr 2 O 3 at temperatures above 760 K. X-ray photoelectron spectra indicate a low CrO 2 content and a binding energy of 579.3 eV for Cr 2 p 3/2 photoelectrons in Cr 2 O 5 . Chromium dioxide was found to stably coexist with Cr 2 O 3 and Cr 2 O 5 in the particles. Magnetic measurements show hysteresis loop shifts in the sample, indicating an exchange bias induced by antiferromagnetic Cr 2 O 3 /Cr 2 O 5 in ferromagnetic CrO 2 . An exchange bias of 9 mT at 5 K and a coercivity of 26.3 mT were observed in the chromium oxide particles containing CrO 2 .