Magnetic Irreversibility in VO₂/Ni Bilayers

The temperature dependence of the magnetic properties of VO₂/Ni bilayers was studied. VO₂/Ni bilayers were grown via magnetron sputtering and their magnetic properties were measured using a Vibrating Sample Magnetometer. VO₂ exhibits a well-known Structural Phase Transition (SPT) at 330-340 K, from a low temperature monoclinic (M) to a high temperature rutile (R) structure. The SPT of VO₂ induces an inverse magnetoelastic effect that strongly modifies the coercivity and magnetization of the Ni films (1). Growth conditions allow tuning of the magnetic properties. Above the transition temperature, Ni deposited on (M) VO₂ shows a coercivity enhancement whereas Ni deposited on (R) VO₂ shows suppression of the coercivity. Samples were cycled several times to check if the changes in coercivity and magnetization were reversible (2). Bilayers with Ni deposited on (R) VO₂ show reversibility, samples with Ni deposited on (M) VO₂ shown an irreversibility after the first SPT. This irreversibility can be associated with cracking of the VO₂ layer as it relieves stress due to the transition and has implications for the resistance versus temperature behavior of the VO₂.

¹ J. Lauzier et al., J. Appl. Phys. 122, (2017).

² J. Lauzier et al., J. Phys. Condens. Matter 30, (2018).