Temperature Dependence of the Exchange Bias Characteristics in a Conventional Magnetic Tunnel Junction

Abstract

The temperature dependence of the exchange bias in magnetic tunnel junctions (MTJs) was measured by using a cryogenic tunneling magneto-resistance (TMR) system and a superconducting quantum interference device (SQUID) at temperatures from 2 K to 300 K. The MTJ device have a typical Ta / NiFe / IrMn / CoFe / AlOx / CoFe / Ta structure. The exchange bias field (H,,) was estimated from the curves of the TMR ratio and the M-H loop measurements with the SQUID were used to confirm the experimental results. The H,, of the typical exchange bias system was gradually increased up to about 10 K for both as-grown and ex-situ-annealed samples. The increase in H-ex with decreasing temperature may be related to a reduction in the interface roughness or to an uncompensated AFM interfacial spin density in the anti-ferromagnetic systems.