Magnetic and electrical transport properties of Ru doped cobalt ferrite thin films with perpendicular magnetic anisotropy

Monalisha Peda,P S Anil Kumar

doi:10.1063/9.0000169

Abstract

Epitaxial ferrimagnetic thin films of (Co, Ru) Fe2O4 were grown on MgO (001) substrate using pulsed laser deposition technique. Ruthenium substitution in cobalt ferrite has increased the conductivity by orders of magnitude, but it has a minimal effect on magnetic properties. The film has a high coercivity and perpendicular magnetic anisotropy (PMA), where the magnetic easy axis points perpendicular to the film surface. We report the magnetic and electrical transport properties here. The temperature variation of resistivity showed different conduction mechanisms at high and low-temperature regimes. Room temperature Hall measurement reveals “n” type carrier with a carrier concentration of 4×1020/cm3. The film showed negative MR and a linear decrement with the magnetic field without any saturation.

Highlights

Room temperature magnetic semiconductors have drawn significant attention due to their potential applications in spin-based spintronic devices such as MRAM,1,2 ferromagnetic field-effect transistor (FET).3–5 The metallic ferromagnetic films having perpendicular magnetic anisotropy (PMA) are primarily used in ultra-high-density magnetic recording.6,7 There is a lack of sufficient oxide-based magnetic semiconductors with PMA
The insulating nature of cobalt ferrite is due to a lack of hopping conduction at the B site, where all Fe ions exist with a +3 valence state
We found that the transport mechanism of the magnetic semiconductor is well understood using the small polaron hopping model and Mott’s variable range hopping (VRH)

Summary

Introduction

Room temperature magnetic semiconductors have drawn significant attention due to their potential applications in spin-based spintronic devices such as MRAM, ferromagnetic field-effect transistor (FET). The metallic ferromagnetic films having PMA are primarily used in ultra-high-density magnetic recording. There is a lack of sufficient oxide-based magnetic semiconductors with PMA. The insulating nature of cobalt ferrite is due to a lack of hopping conduction at the B site, where all Fe ions exist with a +3 valence state. It has a high Curie temperature (Tc ∼860 K) due to antiferromagnetic superexchange interaction between A and B sites. To realize spin-polarized carriers in an oxidebased magnetic semiconductor with PMA, we have substituted Co2+ ion with dopants having a valence state more than +3. Ru doping results in Fe3+/Fe2+ mixed-valence state at B site to maintain charge neutrality This supports the hopping of spin-polarized 3d-t2g electrons and transforms insulating cobalt ferrite to semiconducting. This work demonstrates the potential use of an oxide-based magnetic semiconductor with spin-polarized carriers in spintronics based devices

Methods

Results

Conclusion