Electrical Detection of Millimeter-Waves by Magnetic Tunnel Junctions Using Perpendicular Magnetized L1₀-FePd Free Layer

Abstract

Spin dynamics excited by spin-polarized current in magnetic tunnel junctions (MTJs) is potentially useful in nanoscale electrical oscillation sources and detection devices. A spin oscillator/detector should work at a high frequency, such as that of a millimeter-wave, where the quality of a semiconductor device is restricted by carrier mobility, the CR time constant, and so on. Developers of spin systems for practical use need to find out how to excite spin dynamics (i) in the millimeter-wave region, (ii) with low power consumption (ex: no external magnetic field, low damping material), and (iii) for broad frequency modulation. Here L10-ordered FePd alloy with perpendicular magnetocrystalline anisotropy (PMA) and a low damping constant, 0.007, was used for the free layer in the MTJs, and a homodyne-detected ferromagnetic resonance (FMR) signal was obtained at around 30 GHz together with the possibility of one-octave frequency modulation. The FMR signal in out-of-plane magnetized L10-ordered FePd free layer could be excited without an external magnetic field by injecting in-plane spin polarized alternating current. This study shows the potential utility of L10-ordered alloy materials such as FePt, CoPt, MnAl, and MnGa in a variety of millimeter-wave spin devices.

Enhancement of tunneling magnetoresistance by inserting a diffusion barrier in L1-FePd perpendicular magnetic tunnel junctions

“…[18][19][20][21] L1 0 -FePd has recently been experimentally verified to have a $ 0.002 and K u $ 1.3-1.4 Â 10 7 erg/cm 3 (Refs. 2,22,and 23) and, as reported by Naganuma et al, 24 has demonstrated a 27.0% room temperature (RT) tunnel magnetoresistance (TMR) ratio in partially perpendicular MTJs (p-MTJs) with an in-plane reference layer.…”

Millimeter-Wave Detector Using Magnetic Tunnel Junctions With Perpendicularly Magnetized L1₀-Ordered FePd Free Layer

“…One of the ways to realize a STD detector in the millimeter-wave region is to introduce the materials having large magnetic anisotropy such as L10-ordered alloys as a free layer material in magnetic tunnel junctions (MTJs). In our previous study, [6] 28 GHz was detected. In this study, a further high frequency region will be performed together with reducing the free layer thickness and decreasing the junction size to 100 nm.…”

Influence of flicker noise and nonlinearity on the frequency spectrum of spin torque nano-oscillators

“…More recently, STNOs have also been identified as key elements in the realization of broadband microwave energy harvesting 15 or frequency detection 16 – 18 , and of reconstructing bio-inspired networks for neuromorphic computing 19 , 20 . All these functionalities, often realized in the very same STNO devices, are based on basic spintronic phenomena, such as injection locking to an external rf signal 21 , 22 , synchronization of multiple STNOs 23 – 26 or the spin torque diode effect 16 , 27 – 29 .…”