Effect of interface roughness on the exchange bias for NiFe/FeMn

Abstract

The effect of interface roughness on exchange bias for NiFe/FeMn bilayers is investigated for polycrystalline films and epitaxial films. Three different systems were investigated: polycrystalline Ta (10 nm)/Ni80Fe20 (10nm)/Fe50Mn50 (20 nm) films on oxygen plasma-etched Si(100) or Cu/H–Si(100) and epitaxial Ni80Fe20 (10nm)/Fe60Mn40 (20 nm) films on Cu/H–Si(110). For films grown on plasma-etched substrates, as the etching time is increased, film roughness increases up to 12 nm. For the polycrystalline films grown on ultrathin Cu underlayers, x-ray diffraction shows the fcc (111) texture is greatly reduced as the thickness is increased. The epitaxial Cu/Si(110) buffer layer induces fcc (111) epitaxial growth and modifies the interface morphology. The dependence of exchange bias on roughness for each set of samples is explained in terms of a competition between the interfacial exchange coupling and the af uniaxial anisotropy.

Multiple antiferromagnet/ferromagnet interfaces as a probe of grain-size-dependent exchange bias in polycrystalline Co/Fe50Mn50

“…Despite several decades of intensive investigation there is still no complete consensus as to the origin of exchange bias [1,2], or the large body of phenomena that accompany the exchange-induced anisotropy, such as coercivity enhancement [1,2], training [1,2], and magnetization reversal asymmetry [4,5]. One issue that has been the subject of numerous investigations is that of the microstructure dependence of the exchange bias H E , particularly with regard to the AF layer [1,2,[6][7][8][9][10][11][12][13][14][15][16]. The interest in this issue arises because many exchange bias models predict a strong sensitivity to the existence of defects and disorder [6,[17][18][19][20][21], either at the AF/F interface or in the bulk of the AF layer.…”

Ferromagnetic Resonance and X-Ray Reflectivity Studies of Pulsed DC Magnetron Sputtered NiFe/IrMn/CoFe Exchange Bias

“…For several systems, the H ex seems to be relatively insensitive to the roughness value [7,11], while in others the H ex varies in direct proportion to the roughness [9,10] or indicates an opposite variation [8]. Research has also shown that the relationship between the H ex and the roughness value is totally different for differently prepared samples [12].…”

“…The underlying mechanism and the role of the interface/ bulk structure have been investigated in a variety of EB systems [4][5][6][7][8][9][10][11][12] with different deposition techniques and F/AF materials. However, due to the wide variety of materials and deposition techniques used, the dependence of the EB field (H ex ) on the roughness is still controversial.…”

Bottom and top AF/FM interfaces of NiFe/FeMn/NiFe trilayers

“…This difference in the EB parameters was attributed to distinct AF/FM spin configurations at the respective interfaces; however, the effect of the structural roughness was not taken into account [15,16]. Nevertheless, it has been reported [18] that the EB main parameters depend on several factors, such as: interfacial spin configuration, interface roughness between the FM and AF materials, textures (structural and magnetic), crystalline grain size and AF layer thickness. For example, Lee et al [17] have studied the NiFe (10 nm)/FeMn (30 nm)/NiFe (10 nm) trilayer by magnetization and transmission electron microscoNiFe (TEM) measurements and they have found that the seed and pinned layers have distinct H ex values due to different roughness values at the lower and upper NiFe/FeMn interfaces.…”