I.B. Puchalska

360° and 0° walls in multilayer Permalloy films

Abstract 360° walls have been investigated in Permalloy double films and multilayers with intermediate layers of carbon, prepared by electron beam evaporation and dc triode sputtering. They are nucleated in an easy axis field when a Bloch line in one layer is trapped at an inclusion. To minimise the magnetostatic energy through the layers, the 360° walls are inclined at an angle β

First direct magneto-optical observations of quasi-Néel walls in double permalloy films

Abstract The first observations of quasi-walls have been performed in the double Permalloy layers separated by a thin carbon layer. This structure was brought to light due to the high-resolution Kerr effect with digital contrast enhancement. The experimental results are in good agreement with the theoretical predictions.

Magnetic properties and domain structure studies in dc triode‐sputtered permalloy/carbon multilayer films

Double‐layer and multiple‐layer thin films of permalloy with carbon as a intermediate nonmagnetic spacer were prepared by low‐energy dc triode sputtering. Coupling between the two layers of the double films is investigated on a series of samples with a fixed thickness of permalloy layers (dp = 300 A) and thickness of the carbon layer dc, varying from 0 to 25 A. Thickness dc = 10 A is found to be the limiting value for the carbon layer to be continuous and 20 A for domain structures in the two magnetic films to decouple. Saturation magnetization Ms, uniaxial anisotropy field, Hk, and coercive force Hc of multilayers with dc = 10 A and dp from 50 to 600 A (number of magnetic layers from 12 down to 1) are measured and found consistent with earlier results by other authors. Multiple domain walls in the multilayers are investigated by Lorentz electron microscopy.

Wall transitions in Permalloy double films

The transition from twin walls to superimposed walls and vice-versa, in two-layer laminated Permalloy films has been observed. Pictures of walls and quasiwalls have been taken using the high-resolution Kerr effect. The transition occurs at reproducible values of magnetic field applied in the hard direction of the sample, and experimental results indicate that it takes place due to the motion of Bloch lines along the walls. >

New type of magnetic domains ― the small lozenge type configuration in amorphous thin films

Abstract Small isolated flat domains in the shape of lozenges with in-plane magnetization have been investigated in Co-Ni-P and Co-Ti amorphous layers. Such domains may be used for high density non-volatile shift register memories. Domain observations are made using the longitudinal Kerr effect. Nucleation is obtained either by overcoming the anisotropy field via a locally and temporary applied high field or from splitting a large zigzag domain into isolated lozenges. To stabilize the domains two constant fields having opposite direction are required. By this method stable domains 5 μ m in length have been observed. Experimental curves showing the variation of the length and width of domains for different configurations of the applied fields are presented. The results are compared to numerical computations. The theoretical model is discussed and the role played by the magnetostatic energy emphasized. Finally, theoretical predictions to obtain smaller domains are presented.

Static and dynamic zig‐zag magnetic domains

The zig‐zag domains have been investigated in a static and dynamic state. The materials are NiCoP and CoTi amorphous films 0.15 μm and 0.12 μm thick with a low coercivity. The first part deals with the nucleation and stabilization process. In the second part is described the characteristic motion of the zig‐zag boundaries. It occurs in a bias field applied along the hard direction with an ac field applied simultaneously along the easy axis.

Induced anisotropy and temperature effect on domain structure in GdFe amorphous thin films

Abstract The domain structure in thin obliquely sputtered amorphous GdFe films has been investigated by Lorentz microscopy. The origin of oblique induced anisotropy is discussed and magnetostriction contribution to domain arrangement is emphasized. Temperature effects on domain structure are shown by “in situ” observations in the microscope. The role played by oxidation is stressed.

Influence of planar anisotropy on the domain structure in amorphous and garnet magnetic films

Domain structure in materials with shape anisotropy and ’’skin’’ anisotropy is shown. The influence of the shape anisotropy in Co‐P amorphous film is discussed and the similarity between the domains in amorphous film and non‐amorphous materials such as Permalloy and YIG single cyrstals is pointed out. The influence of the ’’skin’’ anisotropy in the garnets and amorphous material with perpendicular anisotropy is shown. Some examples of domains in garnet with implanted layer, garnet with Permalloy layer and annealed YCo3 films are presented.

Bitter patterns in polarized light: A probe for microfields

This paper discusses the observation of Bitter patterns on YIG films made with a polarizing microscope. The local stray field associated with the domain structure induces a birefringence in the colloid which in turn determines the light intensity I transmitted by the analyzer. Under the conditions of fixed crossed polars, if the local field makes an angle ψ with the polarizer then I=k(1−cos 4ψ). The nature of the birefringence and its effect upon the intensity allows, in principle, a directional map of the stray field pattern to be constructed.

Magnetic and theoretical studies of NiFe layers coupled through a chromium interlayer

Abstract MBE prepared epitaxial Permalloy/Cr/Permalloy trilayers have been investigated by FMR and BH hysteresigraph. The film growth was monitored by Reflection High Energy Electron Diffraction (RHEED) and Auger Electron Spectroscopy (AES) which indicate Frank-Van der Merve growth of the Cr. The dependence of resonant field position and coercivity on the thickness of the Cr interfilm indicates the existence of an oscillatory long range exchange coupling of the Permalloy films. A transfer matrix theory previously used to analyse ferromagnetic coupling between magnetic films has been extended to include antiferromagnetic coupling and is used to interpret the FMR results.