Effect of L12 ordering in antiferromagnetic Ir-Mn epitaxial layer on exchange bias of FePd films

Abstract

Two series of samples of single-layer IrMn and IrMn/FePd bilayer films, deposited on a single-crystal MgO substrate at different IrMn deposition temperatures (Ts = 300–700 °C), were investigated using magnetron sputtering. L12 ordering was revealed for the 30 nm-thick IrMn epitaxial (001) films with Ts ≥ 400 °C, determined by synchrotron radiation x-ray diffractometry (XRD). XRD results also provide evidence of the epitaxial growth of the IrMn films on MgO substrate. Increasing Ts from 400 to 700 °C monotonically increases the ordering parameter of L12 phases from 0.17 to 0.81. An in-plane exchange bias field (Heb) of 22 Oe is obtained in a 10 nm-thick FePd film that is deposited on the disordered IrMn films. As the L12 ordering of the IrMn layers increases, the Heb gradually decreases to 0 Oe, meaning that the exchange bias behavior vanishes. The increased surface roughness, revealed by atomic force microscopy, of the epitaxial IrMn layers with increasing Ts cannot be the main cause of the decrease in Heb due to the compensated surface spins regardless of the disordered and ordered (001) IrMn layers. The change of antiferromagnetic structure from the A1 to the L12 phase was correlated with the evolution of Heb.

Exchange-coupling-induced fourfold magnetic anisotropy in CoFeB/FeRh bilayer grown on SrTiO3(001)

“…Synchrotron methods, such as x-ray magnetic circular dichroism, are usually required to detect them. [41,42] Different from these AFM layers, when FeRh is in the AFM state, a great number of residual FM moments can still be observed to be mostly located at the upper and bottom interfaces. [32] They actually can be viewed as the rotatable uncompensated moments distributed in the AFM matrix and well separate the exchange coupling between the below pinned uncompensated moments and the CoFeB moments.…”

Double Diffraction or ω-Fe Diffraction in Body-Centered Cubic {112}<111>-Type Twinned Martensite

“…Unlike a completely disordered crystal structure, some crystals can have an ordered structure, such as the atomic layers in ABABAB-type stacking structure (hexagonal close-packing (hcp) structure), or diamond-like structure, as shown in Figure a. This kind of ordering structure tends to produce extra (double diffraction) or superlattice peaks in X-ray powder diffraction patterns and electron diffraction patterns. − In Figure b, the double diffraction in electron diffraction patterns can also come from dual-phase or multiphase structure, such as the one from the matrix phase and the other from fine precipitates embedded in the matrix. A twin is commonly regarded as a dual-component system.…”