Large Diode Sensitivity of CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

Abstract

We report on rf current-induced excitation of the ferromagnetic resonance in CoFeB/MgO/CoFeB magnetic tunnel junctions under a perpendicular magnetic field. By choosing an appropriate external field and using an Fe-rich CoFeB free layer, the effective precession of the free layer could be excited. In a measurement of homodyne detection, a large dc output voltage of 180 µV was obtained when an rf signal power of -25 dBm was applied. The sensitivity of this junction, as an rf rectifier, reaches about 170 mV/mW (280 mV/mW after impedance matching correction), which is the same order compared with that of a Schottky diode operated at room temperature.

Microwave detectors based on the spin-torque diode effect

“…(6) gives the resonance STMD sensitivity in the passive regime res 700 V/W, which is comparable to the sensitivity of Schottky diodes [13]. At room temperature T = 300 K and for the measurement bandwidth of f = 1 MHz, Eq.…”

“…In the traditional in-plane (IP) regime of operation of an STMD [12,13,17] the STT excites a small-angle in-plane magnetization precession about the equilibrium direction of magnetization in a free layer (FL) of a magnetic tunnel junction (MTJ) (see the red dashed curve in Fig. 1).…”

“…The resonance sensitivity of a traditional STMD res / DC RF UP is predicted to be approximately 10 4 V/W (see [17]), while the best experimental value achieved to date is res 300 V/W for an unbiased STMD [13]. However, res 12000 V/W has been recently obtained for an STMD biased by a dc current [18].…”

“…The spin-transfer-torque (STT) effect in magnetic multilayers was theoretically predicted in [1,2] and experimentally observed in [3][4][5][6][7][8][9][10][11][12][13]. It provides a new method of manipulation of the magnetization direction in nanomagnetic systems [14]: magnetization switching [3,4], generation of microwave oscillations under the action of a dc electric current [5][6][7][8][9][10][11] and the spin torque diode effect [12,13], which can then be used for the development of practical microwave detectors, so called spin-torque microwave detectors (STMD), and also for quantitatively measuring STT [15,16].…”

New horizons for microwave applications using spin caloritronics

“…The use of microwave sensor, which is a fraction of the size as that of the microwave antenna, can significantly shrink the dimension of the implementation. Recent technique advances have made spintronic and spin caloritronic sensor a promising alternative to traditional microwave sensors for microwave application [15][16][17][18][19][20][21][22][23][24][25][26][27]. To detect the phase of incident microwaves, which plays a crucial role in microwave imaging applications, a rapid microwave phase detection technique has recently been developed based on spin caloritronic microwave sensors [28].…”