Magnetic hardening and exchange bias effect in dual-phase Co3Mn nanowire arrays

Mn-based magnetic alloys and compounds having large magnetic anisotropy are currently focused as alternate materials for various spintronic applications. In this work, magnetization behavior of Co3Mn alloy nanowires (NWs) was investigated by fabricating with well-known template-based electrodeposition method where the electrodeposition was carried out at sinusoidal high voltage. The NWs were annealed at 300 degrees C and 400 degrees C with 10 degrees C/min heating and cooling rate to eliminate the crystal defects caused by high-voltage deposition. Crystal structure analysis displayed the as-deposited NWs were crystallized into a face-centered cubic (fcc) structure with crystallite size 24.93 nm, while the hexagonal close pack (hcp) phase with crystallite size 38.61 nm was induced after annealing. The as-deposited NWs exhibited the soft ferromagnetic behavior with coercivity (HC)=128 Oe and saturation magnetization (MS)=311 emu/cm(3) along axial direction but magnetic hardening induced after annealing with HC=688 Oe and MS=228 emu/cm(3) caused by strong pinning effects and elastic coupling between hcp and fcc phase. Interestingly, the asymmetric shift in MH-loops of annealed NWs was noted below 150 K when the temperature-dependent MH-loops measured after cooling the sample in the magnetic field. This observation confirmed the existence of exchange bias effect in NWs caused by short-range exchange interaction between ferromagnetic fcc phase and antiferromagnetic hcp phase.

Automated summary

Mn-based magnetic alloys are being studied as alternative materials for spintronic applications. The magnetization behavior of Co3Mn alloy nanowires was investigated, showing changes in magnetic properties after annealing and the presence of exchange bias effect at temperatures below 150K.