Anomalous magnetoresistance behavior of CoFe nano-oxide spin valves at low temperatures

Abstract

We report magnetoresistance curves of CoFe nano-oxide specular spin valves of MnIr/CoFe/nano-oxidized CoFe/CoFe/Cu/CoFe/nano-oxidized CoFe/Ta at different temperatures from 300 to 20 K. We extend the Stoner–Wolfarth model of a common spin valve to a specular spin valve, introducing the separation of the pinned layer into two sublayers and their magnetic coupling across the nano-oxide. We study the effect of different coupling/exchange (between the antiferromagnetic layer and the bottom sublayer) field ratios on the magnetization and magnetoresistance, corresponding with the experimentally observed anomalous bumps in low temperature magnetoresistance curves.

Exchange coupling and NOL magnetism consideration in Co1−xFex specular spin-valves

“…Uncovering and understanding of the NOL structure and magnetism in an SPSV are of great interest from the viewpoint of the magnetic exchange coupling through NOL. Recently, the enhancement of exchange field below Ne´el temperature of the NOL after field cooling was reported for Co 0.9 Fe 0.1 -NOL inserted conventional spin valve [2]. This result suggests the existence of an antiferromagnetic (AFM) component in NOL.…”

Thermopower in specular spin valves

“…However, the microscopic physics of electron specular reflection is still incomplete. We recently showed that the NOL is formed by magnetic oxides with a PM-AFM transition below room temperature that can strongly affect transport properties, particularly MR [4,5]. To further study the effects of the NOL on the magneto-transport of SVs we mea- * Corresponding author.…”

Effect of nano-oxide layers on the magnetoresistance of ultrathin permalloy films

“…A spin valve (SV) with nano-oxide layers (NOLs) has attracted much attention due to its important application on read head of a hard disk drive [1][2][3]. Many researches focus on improving properties by controlling its interfacial microstructure [4][5][6][7][8][9][10].…”