Micromagnetism and magnetization reversal of micron-scale (110) Fe thin-film magnetic elements

Abstract

Magnetic force microscope ͑MFM͒ imaging in conjunction with longitudinal Kerr hysteresis loop measurements have been used to investigate the micromagnetic behavior of micron scale epitaxial ͑110͒ bcc Fe thin-film elements ͑50-nm thick͒ with rectangular, triangular, and needle-shaped ends and competing magnetic anisotropies. Thin-film elements of 2-m width and 6-m length and greater have been fabricated with their long axis oriented either parallel or perpendicular to the ͓001͔ in-plane magnetocrystalline easy axis. For elements with their long axis perpendicular to the ͓001͔ direction, the end shape is critical in determining domain nucleation, domain configurations, and magnetic hysteresis. The magnetization reversal mechanisms are revealed by direct field dependent MFM imaging. Magnetic vortex configurations within elements during reversal are seen to be affected by small changes in element corner shape. Similarly, small trapped domains and domain walls are observed to applied fields significantly larger than the coercive field and apparent magnetic saturation field, as determined by hysteresis loop measurements of arrays of elements. These are shown to have a dramatic effect on the character of the low-field magnetic hysteresis. Particles with long axis parallel to the ͓001͔ direction have large remanence and switching fields which also depend sensitively on end shape. The angular dependence of the switching field observed in these elements is contrasted to that of magnetization reversal by coherent rotation.

Structure-induced magnetic anisotropy in the Fe(110)∕Mo(110)∕Al2O3(112¯0) system

“…Therefore, detailed micromagnetic studies are of particular importance for tailoring the magnetic properties of such MRAM cells. This includes experiments on the magnetic switching 7,8 as well as micromagnetic simulations. 9,10 In this context a precise knowledge of magnetic anisotropy energies of the magnetic layers is of outstanding interest.…”

Characterization of epitaxial growth of Fe(110) on (11−20) sapphire substrates driven by Mo(110) seed layers

“…For epitaxial bcc Fe(1 1 0) thin ®lms grown on Al 2 O 3 (1 1 À2 0) substrates using a Mo buer it was already shown that the ®lm demagnetization factors con®ne the magnetization to the (1 1 0) plane [17]. In addition to the cubic magnetocrystaline anisotropy the Fe(1 1 0) plane has a strong inplane strain induced uniaxial anisotropy component along the [0 0 1] direction.…”

“…In addition to the cubic magnetocrystaline anisotropy the Fe(1 1 0) plane has a strong inplane strain induced uniaxial anisotropy component along the [0 0 1] direction. Along the [0 0 1] direction the cubic and uniaxial anisotropy constants have been determined to K l 6:3 Â 10 5 erg/ cm 3 and K u 3:0 Â 10 5 erg/cm 3 , respectively [17]. The ®lms were grown by molecular beam epitaxy (MBE) which allows the controlled thin ®lm growth with sub-monolayer precision and high material purity.…”

Imaging of micro- and nanomagnetic strudures

“…Figure 2 shows an MFM image of microstructured Fe( 11 0) ellipsoid-shaped elements with lateral dimensions of 1.5 flm 500 nm. Starting with a 25 nm thick iron film with (110) orientation these elements have been fabricated by using electron beam lithography and argon ion etching [6]. After applying a magnetic field of 1 Tesla perpendicular to the long axis of the elements -i.e.…”