R. Gemperle

The use of colloid-SEM method for domain observation in CoCrfilms

The aim of this paper is to describe in detail our experience with the colloid-SEM method, especially as far as the colloids are concerned, to summarize the results which we obtained on CoCr films using this method, and to show some advantages and disadvantages of this method in comparison with the digitally enhanced Kerr technique.

Experimental evidence of the magnetic moment of Bloch walls in garnet films

Abstract Differential susceptibility measurements in low in-plane fields showed up a new peak assumed to be caused by magnetization reversal inside the Bloch walls (BW). Highly sensitive measurements carried out subsequently on different domain structures yielded various new parameters such as the BW hysteresis curve, the integral saturated and remanent BW moments and the internal BW coercivity. The mechanism proposed for the observed phenomena is based on the reversible and irreversible motion of Bloch lines inside the Bloch walls.

Stripe and bubble domains in CoCr films

Using the colloid-scanning-electron-microscope (SEM) method, an investigation was conducted of the domain structure of CoCr films (400-1740 nm thick) at different points of the hysteresis loop. In some cases, an AC field exceeding the value of the coercive force was applied in addition to the DC field. For low-coercivity samples (H/sub c//H/sub k/ approximately 0.02) a bubble structure, which is energetically more favorable above a certain critical field, was observed. From the dependence of the bubble density on the DC field the value of the anhysteretic collapse field was estimated and compared with the theory. Attempts were made to observe the field dependence of the domain structure of high-coercivity samples (H/sub c//H/sub k/ approximately 0.08) with different thicknesses. For one sample the results were compared with those determined using the Kerr effect. For thicker films the colloid-SEM method permits the simultaneous observation of the magnetic domains and the columnar structure at the surface of the sample. >

Domain period determination in CoCr films

Abstract Domain structures of two low coercivity ( H c / H k ≈ 0.02) and one medium coercivity ( H c / H k ≈ 0.05) films were observed by the colloid-scanning electron microscopy (SEM) method in d.c. magnetic fields applied normal to the surface. The dependence of the submicron domain period on ascending and descending fields was measured. Anhysteretic curves were obtained by the superposition of a slowly decreasing a.c. field on the given d.c. field. The field dependence of the anhysteretic domain period is compared with the theory of Kooy and Enz. In addition to the visual measurement, the domain period was also determined by a two-dimensional Fourier analysis of the SEM photographs.

Domain observation of a CoCr film by the colloid-sem method

The domain structure of a CoCr film was studied in different magnetic fields using the method of a combination of the colloid technique and scanning electron microscopy (colloid-SEM method). The results obtained are presented and the advantages of this method are discussed.

Magnetization reversal and Bloch lines in bubble domain walls

Abstract The magnetization reversal process in domain walls of bubble lattices in magnetic garnets is investigated visually and photoelectrically. The use of the anisotropic dark-field method allows us to explain the nature of two types of hysteresis loops, i.e. exhibiting single and double jumps. Bubble lattice consisting of χ bubbles (i.e. bubbles in the state S = 1, p = 0) exhibit double-jump hysteresis loops, connected with the transition to the 1H bubble state. Bubble lattices made up of bubbles in the state S = 0, p = 2 exhibit single-jump behaviour.

Domain structures in Co/Pd multilayers

The observations of submicron domain structure of Co/Pd multilayers at various parts of the M-H loop and after different magnetization cycles designed to approach the global-equilibrium domain width are reported. The wall energy densities were estimated from comparison of the measured equilibrium domain width with the anhysteretic model predictions and also compared with the wall energy densities determined from the slope of major M-H loop. >

Double-jump magnetization reversal process in the domain walls of garnet films

Abstract The paper deals with the investigation of the magnetization process inside the Bloch walls of garnet films. Magnetization reversal curves exhibiting two jumps of the magnetization on every branch of the hysteresis loop were found in some samples. The obtained experimental results are discussed in a phenomenological framework.

Structural and magnetic properties of BaCoxTiyFe12−x−yO19 films

Abstract CoTi-doped barium hexaferrite films prepared by pulsed laser ablation deposition, are investigated by XRD, EPMA and VSM magnetometery. The film properties are examined and compared with corresponding quantities measured on single crystals of the same compositions.