Temperature dependent dynamic and static magnetic response in magnetic tunnel junctions with Permalloy layers

TL;DR

This study investigates how temperature affects the magnetic resonance and static properties of magnetic tunnel junctions with Permalloy layers, revealing anomalies near 60K linked to interface stress and magnetic reorientation.

Contribution

It provides new insights into the temperature-dependent magnetic behavior of tunnel junctions with Permalloy, highlighting interface stress effects and magnetic reorientation phenomena.

Findings

Resonance frequency shows a knee-like increase at low temperatures.

An anomaly in magnetization occurs near 60K.

Interface stress induces magnetic reorientation at the Py interface.

Abstract

Ferromagnetic resonance and static magnetic properties of CoFe/Al2O3/CoFe/Py and CoFe/Al2O3/CoFeB/Py magnetic tunnel junctions and of 25nm thick single-layer Permalloy(Py) films have been studied as a function of temperature down to 2K. The temperature dependence of the ferromagnetic resonance excited in the Py layers in magnetic tunnel junctions shows knee-like enhancement of the resonance frequency accompanied by an anomaly in the magnetization near 60K. We attribute the anomalous static and dynamic magnetic response at low temperatures to interface stress induced magnetic reorientation transition at the Py interface which could be influenced by dipolar soft-hard layer coupling through the Al2O3 barrier.