Uniaxial to unidirectional transition of perpendicular interlayer coupling in IrMn/CoFe/NiFeO/CoFe quadrilayers

TL;DR

This study investigates the temperature-dependent transition from uniaxial to unidirectional perpendicular interlayer coupling in IrMn/CoFe/NiFeO/CoFe quadrilayers, revealing a phase change around 55 K linked to magnetic domain behavior.

Contribution

It reports the observation of a temperature-induced anisotropy transition in interlayer coupling and proposes a two-component magnetic scenario in the NiFeOx layer.

Findings

Perpendicular interlayer coupling observed at room temperature.

Transition from uniaxial to unidirectional anisotropy around 55 K.

NiFeOx layer shows a magnetic signal only below 55 K.

Abstract

We studied the interlayer coupling in the quadrilayer consisting of IrMn/CoFe (bottom layer)/NiFeOx/ CoFe (top layer). The in-plane perpendicular interlayer coupling is observed between CoFe layers at room temperature. An anisotropy transition from uniaxial to unidirectional in the perpendicular direction is observed around Tt = 55 K. The nano-oxide layer NiFeOx shows no distinguishable ferromagnetic signal in the high-temperature (uniaxial) phase, while a strong signal appeared in the low-temperature (unidirectional) phase. A possible two-component scenario, that the nano-oxide layer may contain both amorphous short-range antiferromagnetic domains and superparamagneitc clusters, is proposed to explain the phase transition.