Performance of switch between exchange bias and coercivity: Influences of antiferromagnetic anisotropy and exchange coupling

Abstract

• A T -induced 100% switchbetween H Eand H Cin FMCo/AFM multilayers is predicted. • It demonstrates the switchingtemperaturelinearly tuned by K AF. • Theswitching temperaturewidth may be large for big J AF. • The performance of switch depends on uncompensated AFM spin configurations. • A temperature controlledwriting/reading switchis developed. The study on temperature dependence of exchange bias field and coercivity is crucial to solving the writing/reading dilemma in magnetic recording. Motivated by recent experimental findings, a complete switch between exchange bias field and coercivity with temperature is proposed, and the performance, characterized by average switching temperature ( T S ) and switching temperature width (Δ T W ), controlled by antiferromagnetic anisotropy ( K AF ) and exchange coupling ( J AF ) constants is studied based on a Monte-Carlo simulation. The results show that a linear relationship between T S and K AF is established when K AF is above a critical value, while T S is weakly influenced by J AF . On the contrary, Δ T W is insensitive to K AF , while strongly depends on J AF . Besides overcoming thermal energy, the increase of K AF for a small J AF guarantees the completely frozen states in the antiferromagnetic layers during magnetizing at higher temperature, below which the exchange bias field exists with a negligible coercivity. Otherwise, for a large J AF , the uncompensated antiferromagnetic magnetization behavior during the ferromagnetic magnetization reversal becomes complicated, and the switching process in the low temperature range depends on the irreversibility of uncompensated antiferromagnetic magnetization reversal during magnetizing, while in the high temperature range mainly influenced by the field-cooling process, resulting in a large Δ T W . This work provides an opportunity to control/optimize the performance of the temperature-induced switch between unidirectional and uniaxial symmetries through precisely tuning K AF and/or J AF to meet different application demands in the next generation information technology.