Positive exchange bias and inverted hysteresis loop in Y3Fe5O12/Gd3Ga5O12

Abstract

We present evidence of an unprecedented room temperature positive exchange bias (EB) and hysteresis loop inversion in monolithic ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ films grown epitaxially on a (111)-oriented ${\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ crystal. The growth-induced interfacial ${\mathrm{Gd}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ layer couples antiparallel to the ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ layer and leads to positive EB and in-turn loop inversion. An exchange shift as large as ${H}_{EB}\ensuremath{\sim}30{H}_{C}$ is realized at 300 K. We observe a critical field value of ${H}_{CF}\ensuremath{\sim}600$ Oe, above which the hysteresis loop inversion takes place. Our findings may have strong implication for spintronics device applications.