Abstract
Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effects are of interest in a possible application of magnetic sensor elements, such as read-head of hard disk drives. To improve the junction performance, the interface tailoring effects were investigated for the Heulser alloy, Co2Fe0.4Mn0.6Si (CFMS), based CPP-GMR junctions with an -Ag3Mg ordered alloy spacer. Ultra-thin Fe or Mg inserts were utilized for the CFMS/Ag3Mg interfaces, and CPP-GMR at low bias current density, J and the J dependence were evaluated for the junctions. Although, at low bias J, MR ratio decreased with increasing the inserts thickness, the device output at high bias J exhibited quite weak dependence on the insert thickness. The output voltages of the order of 4 mV were obtained for the junctions regardless of the insert at an optimal bias J for each. The critical current density was evaluated by the shape of MR curves depending on J. increased with the insert thicknesses up to 0.45 nm. The enhancement of suggests that spin-transfer-torque effect may reduce in the junctions with inserts, which enables a reduction of noise and can be an advantage for device applications.
Highlights
Current perpendicular to plane (CPP) giant magnetoresistance (GMR) junction is potentially utilized for highly sensitive magnetic sensor applications, e.g., read-head devices for hard disk drives (HDDs) [1,2,3,4]
We can say that an advantage of CPP-GMR is the low RA compared to MgO-Magnetic tunnel junctions (MTJs), which is currently used for HDD
It is confirmed that the epitaxial growth and the L21 phase in the CFMS electrode are maintained for all samples including the samples with Fe or Mg inserts
Summary
Current perpendicular to plane (CPP) giant magnetoresistance (GMR) junction is potentially utilized for highly sensitive magnetic sensor applications, e.g., read-head devices for hard disk drives (HDDs) [1,2,3,4]. A merit of CPP-GMR junction is a relatively low areal resistance (RA) of the order of 10−2 –10−3 Ω·μm , which is an advantage over tunnel magnetoresistance (TMR) junctions. We can say that an advantage of CPP-GMR is the low RA compared to MgO-MTJs, which is currently used for HDD read-heads, and the development of CPP-GMR is necessary for futre HDD tecnology. For realization of high output for the CPP-GMR junctions, magnetic materials with high-spin polarization are essential. One of the developed magnetic material classes for CPP-GMR junctions is half-metallic cobalt (Co)-based Heusler alloys for some of which the theoretically predicted spin polarization is 100% [10]. In experiments for CPP-GMR, a pioneer work has been reported for junctions using Co2 MnSi Heusler alloy and a
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