[10p-Z08-11~17] 10.3 Spin devices, magnetic memories and storages

▲ [10p-Z08-17] Tunnel magnetoresistance sensor devices with amorphous CoFeBTa-based free layers

〇(P)Mahmoud Rasly Eldesouky¹, Tomoya Nakatani¹, Jiangnan Li¹, Hossein Sepehri-Amin¹, Hiroaki Sukegawa¹, Yuya Sakuraba¹ (1.NIMS)

Keywords:Magnetic field sensor, tunnel magnetoresistance, 1/f noise

To improve the magnetic field sensing performance of CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) sensor devices, the CoFeB free layer (FL) is often laminated with soft-magnetic materials such as NiFe. However, the lamination of NiFe above/below CoFeB tends to degrade the TMR ratio because the 111 texture of NiFe propagates to the CoFeB layer. In this study, we introduced an amorphous (Co_0.4Fe_0.4B_0.2)₉₁Ta₉ in the FL of top-pinned spin-valve MTJs, resulting in no influnce on the texture of CoFeB and thereby TMR ratios. Linear R-H curves with a negligible coercivity have been obtained by using two-step annealing technique. The low-frequency properties have been investigated. All sensors showed 1/f noise behaviors. Moreover, we achieved a detectivity as low as ~ 2 nT/Hz^0.5 using a single MTJ sensor and ~ 600 pT/Hz^0.5 using a Wheatstone bridge sensor.