[17p-Z19-8~24] 10.3 スピンデバイス・磁気メモリ・ストレージ技術

▲ [17p-Z19-16] Highly-sensitive tunnel magnetoresistance sensor devices with NiFe/CoFeBTa free layers

〇(PC)Mahmoud Rasly Eldesouky¹、Tomoya Nakatani¹、Yuya Sakuraba¹ (1.NIMS)

キーワード：Magnetic field sensor, tunnel magnetoresistance, 1/f noise

We recently showed tunnel magnetoresistance (TMR) sensors with linear and closed resistance (R)-field (H) curve using a top-pinned spin-valve TMR sensor with CoFeBTa (CFBT) (20)/Ta (0.3)/CoFe (3) free-layer (FL). The sensor’s field detectivity, defined by D = S_v^0.5/(ΔV/ΔH), where S_v is noise voltage density in V/Hz^0.5, ΔV is the full output voltage and ΔH is the operating magnetc field range of the sensor. Our sensor showed D as low as 2.2 nT/Hz^0.5 at 10 Hz. However, the sensor showed a wide ΔH range of 2.5 mT. This means that there is a room to improve D by decreasing ΔH. In this talk, we present a technique to reduce ΔH and improve D by laminating NiFe with CFBT/Ta/CFB FL. Results showed that ΔH is strongly decreased to 1.5 mT by introducing a thin layer of NiFe (≈ 5 nm). Therefore, D improved to the order of ~1.55 nT/Hz^0.5 at 10 Hz, which is lower than we previously reported.