Nanocomposites and nanomaterials

Antiferromagnetic composites for spin electronics
Sohatsky V.P. 
T. Shevchenko National University of Kyiv. Volodymyrska Str., 60,  Kyiv-01601, Ukraine.  E-mail: vso@univ.kiev.ua 

Among the problems of spintronics, which has not yet found a comprehensive solution is remagnetization on the nanoscale and increasing the operating frequencies of the spintronic and/or photonic elements. Composite thin film structures for spintronics have an advantage over monofilms due to combination of several substantial properties that make it possible to remagnetize them not only by a conventional external magnetic field but also by applying mechanical stresses, electric fields or optical irradiation. Our previous studies of mechanically stressed ferrimagnetics of various compositions showed a possibility of changing shape of their hysteresis loops (otherwise operating characteristics of the spin valve sensors) from linear (in analog mode) to almost rectangular (in discrete mode) [1]. Further simulations of remagnetization were performed on the basis of energy balance equations taking into account growing stray fields with decreasing size and coercivity of the nanosized elements. Thus the remagnetization conditions were obtained up to the nanometer spatial elements.
Antiferromagnets (AF) have a significant advantage in remagnetization rate over any other magneto-optical materials due to some non-collinearity of their magnetizations in sublattices. The resulting precession of their magnetic moments leads to fast-changing of spatial orientation of magnetization. Such a remagnetization was studying in AF orthoferrites (Y(Eu, Tm)FeO3) and in iron borate (FeBO3) under applied magnetic field and mechanical stress. Both materials are relevant for magnetooptics in transmission mode, although they have significantly different hysteresis loops, coercivity value (e.g. approx. 10 Oe in YFO and close to 0 in FB). Modelling and experiments with the mentioned materials allowed to determine the nature of their piezomagnetization in a wide frequency range, as well as to measure the magnetic response to the impact of the femtosecond laser pulses. Despite a simplicity of the applied model, it allowed to predict the distribution of magnetization in studied materials with a sufficient accuracy for a lot of specified parameters. 

1.	Sohatsky V.P., Zubenko I., Pokutnii O. Stress sensitivity of nanolayered magnetic sensors // Abstr.of NANO-2018 Intern. Conference-Kyiv, Ukraine.- 2018.- P.258-259.