Abstract
Magnetic properties and phase composition of both MnN/CoFe (MnN at top of bilayer) and CoFe/MnN films (MnN at bottom of bilayer) bilayers through annealing at various temperatures (Ta = 300-450 °C) and then cooling to room temperature under the application of an external magnetic field of 1.5 kOe are compared. The exchange bias field (HE), the magnitude of magnetic hysteresis loop shift, of the studied films is highly related to phase composition of antiferromagnetic (AF) layer. The increase of HE with increasing Ta in the range of 300-375 °C possibly results from the improvement of magnetocrystalline anisotropy of AF related to the promoted crystallinity and stress relaxation of tetragonal face-centered θ-MnN phase. The reduction of HE at higher Ta is due to the decreased volume fraction or disappearance of θ-MnN phase and the formation of impurity phases, such as Mn4N and Mn. The induction of impurity phases is possibly related to the diffusion of part of N out of MnN phase at higher Ta. Higher HE for CoFe/MnN than MnN/CoFe at Ta = 300-375 °C might be attributed to larger amount and higher degree of stress relaxation for θ-MnN phase. For CoFe/MnN film annealed at 375 °C, the highest HE = 562 Oe is attained, and the corresponding interfacial exchange energy of 0.47 mJ/m2 in this study is comparable to that reported by Meinert et al. [Phys. Rev. B 92, 144408 (2015)].
Highlights
Nowadays spin electronics is becoming a significant technology and the foundation of spin-valve based devices, like giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) and so on.1–16 The spin-valve based devices mainly consist of a free layer and a pinned layer
CoFe/MnN and MnN/CoFe films with 5-nm-thick CoFe layer and 40-nm-thick MnN layer were prepared on 10-nm-thick Ta underlayer buffered glass substrates (Corning 1737) at room temperature (RT) by magnetron sputtering at the external in-plane magnetic field of 350 Oe induced by the NdFeB sintered magnet
x-ray diffractometer (XRD) patterns of MnN/CoFe (MnN at the top layer) and CoFe/MnN (MnN at the bottom layer) films annealed at different temperature (Ta) within the applied magnetic field of 1.5 kOe are shown in Fig. 1(a) and (b), respectively. θ-MnN(002) phase is found in both as-deposited films, while no diffraction peak from CoFe and Ta layers is detected due to too thin thickness
Summary
Nowadays spin electronics is becoming a significant technology and the foundation of spin-valve based devices, like giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) and so on. The spin-valve based devices mainly consist of a free layer and a pinned layer. The spin-valve based devices mainly consist of a free layer and a pinned layer. AF MnN crystallizes at θ phase with tetragonal face-centered NaCl structure at room temperature (RT).. Its. TN is about 660 K where this magnetic transition accompanies with a phase transformation from tetragonal to cubic.. Magnetic properties of MnN-based exchange bias system have been studied by Meinert.. For perpendicular MnN/CoFeB/MgO/Ta films, HE of 3600 Oe could be attained for ultrathin thin CoFeB layer of 0.65 nm in thickness.. We compare magnetic properties and phase composition of both MnN/CoFe (MnN at top of bilayer) and CoFe/MnN (MnN at bottom of bilayer) films with various annealing temperatures (Ta) in the range of 300-450 ○C under the application of an external magnetic field of 1.5 kOe For perpendicular MnN/CoFeB/MgO/Ta films, HE of 3600 Oe could be attained for ultrathin thin CoFeB layer of 0.65 nm in thickness. As EB effect is mostly an interface phenomenon, EB field (HE) is highly sensitive to interface roughness, morphology, crystallinity, thickness and grain size of both FM and AF. In this work, we compare magnetic properties and phase composition of both MnN/CoFe (MnN at top of bilayer) and CoFe/MnN (MnN at bottom of bilayer) films with various annealing temperatures (Ta) in the range of 300-450 ○C under the application of an external magnetic field of 1.5 kOe
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