Magnetic Anisotropy Engineering in Thin Film Ni Nanostructures by Magnetoelastic Coupling

Abstract

A phenomenon that can be exploited for the manipulation of magnetization without the conventional current-generated magnetic fields is magnetoelastic coupling, which might, thus, pave the way for lowpower data-storage devices. Here, we report a quantitative analysis of the magnetic uniaxial anisotropy induced by piezoelectric strain in Ni nanostructured squares. By applying strain, the magnetic domains in Ni nanostructured squares can be manipulated by the magnetoelastic effect in the Ni. The strain-induced anisotropy displaces the domain walls in the square leading to changes in the domain sizes. By comparing the experiments with micromagnetic simulations, the resulting uniaxial anisotropy is quantified. We find a good agreement for a magnetostrictive constant of λ s ¼ −26 ppm, confirming a full strain transfer from the piezoelectric to the Ni nanostructures and the retainment of a bulklike λ s .

Electric field modification of magnetotransport in Ni thin films on (011) PMN-PT piezosubstrates

“…The (011) cut is particularly suitable because of the possibility of obtaining a high and well-defined uniaxial anisotropy by inducing simultaneously compressive and tensile strains in orthogonal [100] (x) and [011] (y) in-plane directions due to the different signs of d 31 and d 32 piezocoefficients. 5,13 Voltage control of magnetization has been widely studied for Ni films on (011) PMN-PT using magneto-optic Kerr effect (MOKE) magnetometry and magnetic imaging, [7][8][9]11 whereas the electric field effects on the MR have only been studied in detail for magnetite 16,20 and permalloy films 17 on (011) PMN-PT. Additionally, the MR response of permalloy films as a function of the electric field applied to the (011) PZN-PT piezosubstrate has been reported.…”

“…2 There are numerous reports on voltage control of magnetization (see, e.g., reviews, 1-4 references therein, and recent Refs. 5 11), whereas for electric field effects on the anisotropic [12][13][14][15][16][17][18][19][20] and giant 13,21,22 [4][5][6][7][8][9][10][11]13,14,16,17,20 In such structures, upon application of an electric field, the piezoactive substrate induces a strain in the ferro(i)magnetic film and hence modifies its magnetic properties due to the magnetoelastic coupling effect. The (011) cut is particularly suitable because of the possibility of obtaining a high and well-defined uniaxial anisotropy by inducing simultaneously compressive and tensile strains in orthogonal [100] (x) and [011] (y) in-plane directions due to the different signs of d 31 and d 32 piezocoefficients.…”

MFM Study of the Domain Structure of Permalloy Microparticles under Mechanical Stress

“…The studies were carried out on samples representing an array of the planar Py (Ni79%, Fe16%, Mo4%) particles (with the size of 25×25×0.03 μm 3 ) located on a glass substrate. Before forming the particles, the glass substrate was coated with a thin copper film (~5 nm) for discharging the sample during measurements by the magnetic force microscope (MFM).…”

“…The following formula H a =2k eff /M S , where M s is the saturation magnetization of the Py particle, was used. A similar approach was used in [3] to determine the magnetization distribution in Ni particles under mechanical stress.…”

“…Recently the possibility of using the Villari effect (the change of magnetic properties of a body under mechanical impact) for the magnetic reversal processes of micro and nanostructures is intensively studied [1][2][3][4]. This is due to the possibility of a significant reduction in the energy required for re-writing a single bit of information due to the simultaneous use of a magnetic field and mechanical stress.…”