Abstract
We report on the perpendicular magnetic anisotropy (PMA) behavior of heavy metal (HM)/Fe alloy/MgO thin film heterostructures when an ultrathin HfO2 passivation layer is inserted between the Fe alloy and MgO. This is accomplished by depositing one to two atomic layers of Hf onto the Fe alloy before the subsequent rf sputter deposition of the MgO layer. This Hf layer is fully oxidized during the subsequent deposition of the MgO layer, as confirmed by X-ray photoelectron spectroscopy measurements. The HfO2 insertion generates a strong interfacial perpendicular anisotropy energy density without any post-fabrication annealing treatment, for example, 1.7 erg/cm2 for the Ta/Fe60Co20B20/HfO2/MgO heterostructure. We also demonstrate PMA even in Ni80Fe20/HfO2/MgO structures for low-damping, low-magnetostriction Ni80Fe20 thin films. Depending on the choice of the HM, further enhancements of the PMA can be realized by thermal annealing to at least 400 oC. We show that ultra-thin HfO2 layers offer a range of options for enhancing the PMA properties of magnetic heterostructures for spintronics applications.
Highlights
We report on the perpendicular magnetic anisotropy (PMA) behavior of heavy metal (HM)/Fe alloy/MgO thin film heterostructures when an ultrathin HfO2 passivation layer is inserted between the Fe alloy and MgO
We show that ultra-thin HfO2 layers offer a range of options for enhancing the PMA properties of magnetic heterostructures for spintronics applications
The realization of robust perpendicular magnetic anisotropy (PMA) in heavy metal (HM)/Fe alloy/MgO thin-film heterostructures,1,2 where typically the Fe alloy is Fe80xCoxB20 (FeCoB), has enabled a pathway for the implementation of high density memory elements based on the spin transfer torque switching of perpendicularly magnetized tunnel junctions (MTJs)
Summary
We report on the perpendicular magnetic anisotropy (PMA) behavior of heavy metal (HM)/Fe alloy/MgO thin film heterostructures when an ultrathin HfO2 passivation layer is inserted between the Fe alloy and MgO.
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