Magnetic irreversibility in VO₂/Ni bilayers

Abstract

We studied the temperature dependence of the magnetic properties of VO/Ni bilayers. The Ni films were deposited on either monoclinic or rutile phase VO. The temperature induced VO transformation from a monoclinic to a rutile structure induces strain in the Ni film. Due to an inverse magnetoelastic effect the coercivity of the Ni films is strongly modified. Both Ni films show strong enhancement of the coercivity near the transition temperature. The coercivity enhancement of Ni is associated with the phase coexistence observed in the VO first order phase transition. Above the transition temperature, Ni deposited on monoclinic VO shows a coercivity enhancement whereas Ni deposited on rutile VO shows suppression of the coercivity. The samples were cycled several times to check if the changes in coercivity were reversible. While samples with Ni deposited on rutile VO show reversibility, samples with Ni deposited on monoclinic VO shown an irreversibility after the first structural phase transition. This irreversibility can be associated with cracking of the VO layer as it relieves stress due to the transition and has implications for the resistance versus temperature behavior of the VO.

Optically Induced Phase Change for Magnetoresistance Modulation

“…Interestingly, the M ‐ T curve shows an abnormal valley in the temperature range where the resistance of VO 2 drops intensely. This phenomenon can be explained by the phase coexistence of the nonmagnetic layer (for example, the VO 2 layer in this work) . The uniform phase change of VO 2 can enhance the magnetization in a gradual way.…”

Surface and Electrical Characterization of Bilayers Based on BifeO₃and VO₂

“…In thin film form, the FE and AF order parameters of multiferroics could be affected for the phenomenon of magnetostriction [1]- [4] due to the change in the dimensions of the material as a consequence of stresses generated at the contact interface, either with the substrate or with another material. To study this mechanism of coupling at the interface with BFO, the vanadium dioxide (VO2) system was used, which has been widely analyzed due to the structural change it undergoes from VO2 (monoclinic) to VO2 (tetragonal) at a temperature of 340 K, showing weak ferromagnetic behavior [6], [7]. The combination of these materials in heterostructures gives access to the study of mixed properties and their control.…”

“…Good compatibility might therefore be expected in the bilayer system based on BFO and VO2 since the interface effects are predominant and detectable in analogous materials [8]. de la Venta et al, [6], [7], [9], [10] showed the change in the coercivity of thin films of nickel deposited on V2O3 and VO2, a change attributed to the structural phase transition of V2O3 and VO2. Saerbeck et al, [11] studied and compiled information about the coupling between magnetism and the structural phase transition by interfacial tension in different systems of La0.7A0.3MnO3 (A = Sr,Ca), Fe3O4, CoFe2O4, FeRh, Ni, Fe and Co, using as a base the structural change in the VO2, V2O3 and BaTiO3 compounds, resulting in structures with hybrid properties that manage to modify and/or control the magnetic behavior through effects of tension and inverse magnetostriction.…”

Surface and Electrical Characterization of Bilayers Based on BiFeO3 and VO2

“…To study this mechanism of coupling at the interface with BFO, the vanadium dioxide (VO 2 ) system was used, which has been widely analyzed due to the structural change it undergoes from VO 2 (monoclinic) to VO 2 (tetragonal) at a temperature of 340 K, showing weak ferromagnetic behavior [ 12 , 13 ]. The combination of these materials in heterostructures gives access to the study of mixed properties and their control.…”