Nanocomposites and nanomaterials

Enhanced magnetic anisotropy in small-sized elliptical synthetic-antiferromagnets
Borynskyi V.Yu.1, Polishchuk D.M.2, Melnyk A.K.3, Kravets A.F.1, Tovstolytkin A.I.1, Korenivski V.2
1 Institute of Magnetism of the NAS of Ukraine and MES of Ukraine. Akad. Vernadsky blvd., 36-b, Kyiv-03142, Ukraine. 
E-mail: vladislav.borinskiy@gmail.com
2 Nanostructure Physics, Royal Institute of Technology. Hannes Alfvénsväg, 12, Stockholm-10691, Sweden. 
3 Institute for Sorption and Problems of Endoecology of the NAS of Ukraine. Naumov str., 13, Kyiv-03164, Ukraine.

Our recent research has shown how both geometry and multilayered structure of synthetic-antiferromagnet (SAF) nanodisks can effectively modify the dynamics of standing spin waves inherent to such systems [1]. In the present work, we want to emphasize the importance of nanomagnet shape considering arrays of elliptical SAF nanostructures, which possess the average major-axis length of 75 nm.
Using the ferromagnetic resonance technique, we obtained a set of spectra for different directions of external magnetic field applied in the plane of the fabricated array. Despite common multi-mode spin-wave resonance, generally governed by magnetostatic interactions within ferromagnetic nanoelements, each spectrum revealed only one resonance line. This behavior originates from the exchange energy contribution that prevails in small-sized elements [2].
In addition, the resonance field of the single mode shifts up by 700 Oe for the 90° magnetization direction, implying strong influence of the individual SAF’s shape. However, analytical calculations evidence that corresponding unidirectional anisotropy is rather enhanced by the SAF-specific spin excitation type. 

1.	Borynskyi V. Yu., Polishchuk D. M., Melnyk A. K., Kravets A. F., Tovstolytkin A. I., Korenivski V. Higher-order ferromagnetic resonances in periodic arrays of synthetic-antiferromagnet nanodisks // Appl Phys Lett.-2021.-119.-P. 192402.
2.	Carlotti G. Pushing down the lateral dimension of single and coupled magnetic dots to the nanometric scale: Characteristics and evolution of the spin-wave eigenmodes // Appl Phys Rev.-2019.-6.-P. 031304.