Enhancement of exchange bias in Ir–Mn/Co_0.9Fe_0.1bilayers by inserting an ultra-thin Co_0.6Fe_0.4layer

Abstract

The exchange biasing of Co0.9Fe0.1 film by the antiferromagnet Ir–Mn via a thin intermediate Co0.6Fe0.4 layer was investigated. It has been found that the exchange bias is drastically enhanced with the insertion of an ultra-thin Co0.6Fe0.4 layer at the interface between Co0.9Fe0.1 and Ir–Mn layers. For the Ir0.25Mn0.75(100 Å)/Co0.9Fe0.1(150 Å) bilayer, the pinning field at room temperature is raised from 92 to 206 Oe when a 4 Å Co0.6Fe0.4 layer is introduced at the interface, and further enhanced to 262 Oe with a 10 Å Co0.6Fe0.4 insertion layer. The corresponding unidirectional anisotropy increases from 0.18 to 0.4 erg cm−2 and reaches a value of 0.54 erg cm−2. The extra large unidirectional anisotropy is maintained as the Co0.6Fe0.4 thickness exceeds 10 Å. The high blocking temperature of the Ir–Mn/Co0.9Fe0.1 bilayer is unaffected by the insertion of the Co0.6Fe0.4 layer. The present results indicate that exchange bias is essentially determined by interfacial spins and, most importantly, the performance of the exchange bias system Ir–Mn/Co0.9Fe0.1, which is commonly used in spin valve giant magnetoresistance devices, can be greatly promoted by the insertion of an ultra-thin interfacial Co0.6Fe0.4 layer.

Large perpendicular exchange bias in IrMn/CoFe/[Pt/Co] multilayers grown on a Ta/Pt buffer layer

“…As is known, the exchange bias of IrMn/Co 100−x Fe x bilayers with the in-plane anisotropy strongly depends on the Co-Fe composition, and the maximum unidirectional anisotropy is at x = 30-40 [12]. It has been further demonstrated that the in-plane exchange bias of IrMn/Co 90 Fe 10 bilayers is tripled with the insertion of a thin Co 60 Fe 40 0022-3727/09/115002+05$30.00 layer at the interface [13]. In this paper, we systematically investigated the PEB of the bottom pinned IrMn/[(Co/Pt) 3 ] and IrMn/Co 60 Fe 40 /[(Pt/Co) 2 ] multilayer films, and found a further twofold enlargement of the PEB in the optimized IrMn/[Co/Pt] multilayer when a thin Co 60 Fe 40 layer replaces the Co layer adjacent to IrMn.…”

Effect of grain size on magnetic and nanomechanical properties of Co60Fe20B20 thin films

“…Magnetic CoFeB, Co, or NiFe thin film can be inserted as a free and/or pinned layer into the MTJ device, as it has a high spin tunneling efficiency and its spin-valve structure exhibits ferromagnetism (FM)/antiferromagnetism (AFM) exchange-biasing anisotropy [7][8][9][10]. Moreover, the favorable characteristics of the MTJ device, including high tunneling magnetoresistance (TMR), strength, and durability, are critical to operation of an MTJ device at room temperature (RT) and in high-temperature environments [11,12].…”

Large enhancement of magnetic damping in the presence of domain walls in spin valves

“…To clearly separate different physical mechanisms of magnetic damping in spin valves, we have studied the magnetic damping in the exchange-biased spin valve IrMn/CoFe/Cu/CoFeB. Benefitting from the large exchange-biased field (∼560 Oe) between IrMn and CoFe [26], we have convincingly revealed the magnetic dynamical property variation of the free CoFeB layer in various magnetic configurations with a sufficient field window for each configuration. We have observed that the CoFeB layer damping constant varies very little between the parallel and antiparallel configurations, but in the intermediate states of the pinned CoFe layer during its magnetization reversal, where multi-domains in the CoFe layer are confirmed, the damping constant exhibits significant enhancement together with a small resonance frequency shift.…”