Improved exchange coupling between ferromagnetic Ni-Fe and antiferromagnetic Ni-Mn-based films

Abstract

Dc magnetron sputtered Ni-Mn and Ni-Mn-Cr films are demonstrated to exhibit strong and thermally stable antiferromagnetism, as well as high corrosion resistance. For a 25.2 nm thick 53.3 Ni-46.7 Mn (in atomic percent) film deposited on top of a 28.5 nm thick 81 Ni-19 Fe film, a unidirectional anisotropy field (HUA) of 120.6 Oe is obtained at room temperature after annealing in vacuum. The equivalent interfacial exchange coupling energy (JK) is 0.27 erg/cm2, three times higher than that of bilayer Ni-Fe/50Fe-50Mn films. This strong exchange coupling appears correlated with the presence of an antiferromagnetic θ (NiMn) phase with a CuAu-I-type ordered face-centered-tetragonal structure. The blocking temperature, at which the exchange coupling disappears, is higher than 400 °C. The Cr addition to the Ni-Mn film dilutes the exchange coupling, but the JK for the Cr content ≤10.7 at. %, is still higher than that of the Ni-Fe/Fe-Mn films. Both Ni-Mn and Ni-Mn-Cr films exhibit corrosion behaviors much better than the Fe-Mn film and comparable to the Ni-Fe film. The films are proposed as longitudinal bias layers for the stabilization of magnetoresistive read sensors.

Induced ordering in electrodeposited nanocrystalline Ni–Mn alloys

“…The spectacular increase in the bit density of magnetic disks has been achieved by giant magnetoresistance and spin valve reading heads, that require soft ferromagnetic thin films with acceptable corrosion resistance, as in NiMn films. 4,5 Further, inverse magnetocaloric effect has been reported in a number of Ni-Mn based systems. 6 Since the as-prepared films show disordered structure, prolonged annealing treatments are generally required to get the ordered structure ͑L1 2 ͒ and exploit their characteristic properties.…”

Paramagnetic to antiferromagnetic phase transformation in sputter deposited Pt–Mn thin films

“…8 Some of these requirements include a high pinning field at the operating temperature of the device ͑approximately 120°C), 9 a high blocking temperature ͑i.e., the temperature at which the pinning field drops to zero͒, good corrosion resistance, and low cost. One class of AFM materials that can meet these requirements are the L1 0 ordered tetragonal alloys, 8,[10][11][12][13][14] such as NiMn and PdMn. Another material from this class, PtMn, has emerged as a promising candidate for exchange biasing.…”

Exchange Bias and Spin-Valve Giant Magnetoresistance in Multilayers with Mn-17 mol%Ir-2 mol%Pt Antiferromagnetic Layer

“…1,2) We have developed a ternary AFM material of Mn-17 mol%Ir-2 mol%Pt 3) which showed the larger exchange bias field (H ex ), the higher thermal stability and the better chemical resistance than Mn-Ir AFM material. Mn-17 mol%Ir-2 mol%Pt is a disordered phase (face centered crystal structure), 3) which doesn't need any annealing process at a high temperature.…”