90° magnetic coupling in a NiFe/FeMn/biased NiFe spin valve investigated by polarised neutron reflectometry
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Date
2014-02-05
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Australian Institute of Physics
Abstract
We have used the PLATYPUS reflectometer at ANSTO to perform polarised neutron reflectometry in order to investigate 90° magnetic coupling in a Ni81Fe19/Fe50Mn50/biased Ni81Fe19 spin valve system. Spin valves play an important role in current and developing technological systems, such as spintronics devices or magnetoresistive sensors. For the later usage, perpendicular coupling in a spin valve structure leads to a desired linear, reversible resistance response to an applied magnetic field. The spin valve presented here consists of both free and exchange biased ferromagnetic Ni81Fe19 layers, the later of which is pinned by an antiferromagnetic Ir25Mn75 layer at low applied magnetic fields. The free Ni81Fe19 may be magnetically reversed under low fields, and standard magnetometry measurements on similar systems have suggested perpendicular orientation of the free and biased magnetisations at zero field. Magnetometry measurements, however, are only capable of providing information about the magnetisation within a sample along the direction of the applied field. In contrast, polarised neutron reflectometry (PNR) is capable of resolving the in-plane magnetisation vectors both along and perpendicular to the applied magnetic field as function of layer depth. Here, PNR was used to obtain magnetic vector depth profiles of the spin valve at several applied fields, including low fields near the switching point of the free Ni81Fe19 layer. At these fields a large spin-flip signal was observed in the free layer, indicating magnetisation aligned perpendicular to the external field applied along the pinned layer magnetisation. Both the non-spin flip and spin-flip signals were also tracked around the free layer hysteresis loops and can be used to map the evolution of the free Ni81Fe19 layer during magnetic reversal.
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Keywords
Beams, Control equipment, Elements, Flow regulators, Magnetic field configurations, Magnetic materials, Metals, Orientation, Transition element compounds, Transition elements
Citation
Callori, S. J., Zhu, T., & Klose, F. (2014). 90° magnetic coupling in a NiFe/FeMn/biased NiFe spin valve investigated by polarised neutron reflectometry. Poster presented to the 38th Annual Condensed Matter and Materials Meeting 2014, Waiheke Island Resort, Waiheke, Auckland, New Zealand; 4th February - 7th February, 2014. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2014/Wagga2014proceedings.pdf