Thickness dependence of the magnetic properties of ripple-patterned Fe/MgO(001) films

Abstract

Grazing incidence Xe + ion sputtering was used to create a nanoscale ripple pattern on a thin Fe film, epitaxially grown on MgO(001). The Fe film has a thickness gradient of 0-20 nm and a ripple height of about 3 nm, giving rise to a transition from a continuous film to separated nanorods with decreasing film thickness. This allowed the investigation of the competition between the uniaxial and biaxial anisotropy of the irradiated sample as a function of thickness. From magneto-optical Kerr effect measurements, we determine accurately the cubic magnetocrystalline anisotropy and the uniaxial anisotropy that originates from the ripple pattern using a coherent rotation model. Our results show that the uniaxial anisotropy strength increases, whereas the contribution of the biaxial crystal anisotropy decreases, when going from the continuous film to the nanorod structures.

Spin-wave nonreciprocity and magnonic band structure in a thin permalloy film induced by dynamical coupling with an array of Ni stripes

“…Roughness changes the conditions for magnetization dynamics locally at the interface, which effectively can change a magnetic anisotropy on the Py surface. 38,39 Let's assume, that at the bottom surface of Py film (at the interface with Cr/Ni) small surface magnetic anisotropy is induced, which results in pinning of the magnetization dynamics. To test the influence of the surface anisotropy, we performed computations with the Rado-Weertman boundary condition 40 superimposed on the dynamic part of the magnetization vector at the bottom surface of Py film (Fig.…”

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

“…Ion-induced surface ripples on ferromagnetic thin films were found to create a tunable pronounced magnetic texture [9][10][11][12][13][14]. So-called wave-ordered nanostructures generated by lowenergy nitrogen ion irradiation of Si were investigated as periodic nanomasks to dope the channel region of field-effect transistors [15].…”

Magnetic states in low-pinning high-anisotropy material nanostructures suitable for dynamic imaging

“…The energy differences F s,oop − F 0 and F s,ip − F 0 can be determined by calculating the saturation energies E s,oop and E s,ip , respectively, from the measured hysteresis loops. 36 Combining these considerations, we arrive at…”

“…30,31 To calculate the crystal field uniaxial anisotropy constant K u , we make use of the analytic relation H = ∂F μ 0 ∂M between the magnetic field H and the magnetization M through the free energy density F , which holds if the system is in thermodynamic equilibrium. 36 In absence of any further knowledge of the magnetization reversal mechanism, the equilibrium magnetization can be approximated by the average of both hysteresis branches, with the difference giving a reasonable estimate for the 2σ confidence interval. The free energy density is a potential, for which we can hence choose a constant offset such that the free energy density of the in-plane saturated state is F s,ip = 0.…”