Abstract
Thin-film strontium ferromolybdate is a promising material for applications in room-temperature magnetic tunnel junction devices. These are spin-based, low-power-consuming alternatives to CMOS in non-volatile memories, comparators, analog-to-digital converters, and magnetic sensors. In this work, we consider the main tasks to be solved when creating such devices based on strontium ferromolybdate: (i) selecting an appropriate tunnel barrier material, (ii) determining the role of the interface roughness and its quantification, (iii) determining the influence of the interface dead layer, (iv) establishing appropriate models of the tunnel magnetoresistance, and (v) promoting the low-field magnetoresistance in (111)-oriented thin films. We demonstrate that (i) barrier materials with a lower effective electronegativity than strontium ferromolybdate are beneficial, (ii) diminution of the magnetic offset field (the latter caused by magnetic coupling) requires a wavy surface rather than solely a surface with small roughness, (iii) the interface dead-layer thickness is of the order of 10 nm, (iv) the tunnel magnetoresistance deteriorates due to spin-independent tunneling and magnetically disordered interface layers, and (v) antiphase boundaries along the growth direction promote the negative low-field magnetoresistance by reducing charge carrier scattering in the absence of the field.
Highlights
Strontium ferromolybdate (Sr2 FeMoO6-δ —SFMO) double perovskites are promising candidates for magnetic electrode materials for room temperature (RT) spintronics applications because they present a half-metallic character, a high Curie temperature (TC ) of about 415 K, and low-field magnetoresistance (LFMR) [1].A magnetic tunnel junction (MTJ) consists of two ferromagnetic (FM) or ferrimagnetic layers separated by a thin insulator serving as a tunneling barrier
We demonstrate that (i) barrier materials with effective electronegativity lower than that of SFMO are beneficial, (ii) diminution of the magnetic offset field requires a wavy rather than solely a smooth surface, (iii) the dead layer (DL) has a thickness in the order of 10 nm, (iv) the tunnel magnetoresistance (TMR) deteriorates due to spin-independent tunneling and magnetically disordered interface layers, and (v) antiphase boundaries along the growth direction promote negative LFMR
SFMO thin films grown by pulsed laser deposition (PLD) on STO (111) substrates exhibit a larger LFMR effect in (111)-oriented films compared to those with the (001) orientation [60]
Summary
Strontium ferromolybdate (Sr2 FeMoO6-δ —SFMO) double perovskites are promising candidates for magnetic electrode materials for room temperature (RT) spintronics applications because they present a half-metallic character (with theoretically 100% polarization), a high Curie temperature (TC ) of about 415 K (ferromagnets should be operated in their ordered magnetic state below TC ), and low-field magnetoresistance (LFMR) [1]. If the two magnetizations have parallel orientations, electrons will tunnel through the insulating layer, and the device is in the low-resistance state If they have antiparallel orientations, practically no tunneling occurs (the high-resistance state) when one of the spin states, spin-up or spin-down, is dominating at the Fermi level. We demonstrate that (i) barrier materials with effective electronegativity lower than that of SFMO are beneficial, (ii) diminution of the magnetic offset field (the latter caused by magnetic coupling due to interfacial roughness) requires a wavy rather than solely a smooth surface, (iii) the DL has a thickness in the order of 10 nm, (iv) the TMR deteriorates due to spin-independent tunneling and magnetically disordered interface layers, and (v) antiphase boundaries along the growth direction promote negative LFMR by reducing charge carrier scattering in the absence of the field
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