Structural, magnetic, and thermal stability of IrMn exchange biased layers

Abstract

The magnetic domain structure, magnetic properties, and thermal stability of IrMn biased top spin valves containing Co and NiFe have been investigated. The magneto-optical indicator film pictures of Ni–Fe biased IrMn spin valve show the formation and motion of domain walls that separate large domains in the free film unlike the Co biased IrMn spin valve structure with many small microdomains. From the angular dependence of the ferromagnetic resonance linewidth (ΔH) and resonance field (Hres) it was found that the IrMn biased Co film is very different from the behavior of a NiO biased Permalloy film which exhibits two-magnon scattering. To investigate the thermal stability two kinds of magnetoresistance measurements at anneal temperature (TAnn) and room temperature (TRT) following anneals were accomplished.

Effects of annealing on the GMR and domain structure stabilization in a Py/Cu/Py/MnIr spin valve

“…One can see that up to T ANN ¼ 360 C the shape of the loops is nearly unchanged, but the maximum MR ratio has decreased significantly. The MR ratio maximums decreased rapidly following annealing above 260 C [5]. Despite the large changes in MR ratio, the H EX (B30 T) and H C (B4.5 mT) values were essentially unchanged at for each T ANN : The loop shape after a 390 C anneal (Fig.…”

“…In recent publications, [1][2][3][4][5][6], it was revealed that diffusion of constituent atoms such as Mn and Ni over the existing layers during annealing results in a decrease of the GMR. In the present work, we report on domain imaging studies of the effects of annealing on the spinvalves (SVs) magnetic domain structure and magnetization reversal process as well.…”

“…The MOIF measurements on the as-deposited SV yield pictures typical for FM coupling with magnetization reversal by nucleation and growth of domains with antiparallel magnetic moments [5]. Fig.…”

“…In the present work, we report on domain imaging studies of the effects of annealing on the spinvalves (SVs) magnetic domain structure and magnetization reversal process as well. The main purpose of these experiments is to find relationships between changes in the magnetic structure upon annealing and changes in the magnetotransport properties.The sample consists of an epitaxial structure of Ni 81 Fe 19 (3 nm)/Cu(2.5 nm)/Ni 81 Fe 19 (3 nm)/Ir 20 Mn 80 (10 nm) deposited by magnetron sputtering onto Si substrate with native oxide that was buffered and caped with 5 nm Ta [5]. The bottom ferromagnetic (FM) layer was ''free,'' and the top layer was exchange biased by unidirectional anisotropy field H EX and an enhanced coercivity H C through coupling to the antiferromagnetic (AFM) IrMn layer.…”

“…The sample consists of an epitaxial structure of Ni 81 Fe 19 (3 nm)/Cu(2.5 nm)/Ni 81 Fe 19 (3 nm)/Ir 20 Mn 80 (10 nm) deposited by magnetron sputtering onto Si substrate with native oxide that was buffered and caped with 5 nm Ta [5]. The bottom ferromagnetic (FM) layer was ''free,'' and the top layer was exchange biased by unidirectional anisotropy field H EX and an enhanced coercivity H C through coupling to the antiferromagnetic (AFM) IrMn layer.…”