Microstructure/magnetic property relationships in CoCrPt magnetic thin films

Abstract

Microstructural investigations of CoCrPtICr andCoCrPt/CrV magnetic thin film media were conducted in order to explain improved media performance as a function of increased Cr concentration in the magnetic layer and a predeposition treatment of the Nip plated AI substrate. Using High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Diffraction Patterns (SADP) it was found that for both underlayer structures, no significant microstructural differences (such as grain size, stacking fault density, orientation, crystalline phase, and bi-crystals) exist between samples grown with 13% Cr and 22% Cr. This indicates that Cr segregation to grain boundaries is the most likely mechanism for improved S/N ratio and higher coercivity. The increased coercivity observed in the treated samples is consistent with an increased grain size in the magnetic layer due to larger Cr underlayer grains

Pinning effect of the grain boundaries on magnetic domain wall in FeCo-based magnetic alloys

“…1,2 They are good candidates for high temperature applications such as new generation turbine engines 3 as well as in recording media where high saturation magnetization is required. 4,5 Many magnetic properties of bulk alloys are closely related to the microstructure. For example, the shape of the hysteresis loop, the coercive field H c , and the initial magnetic permeability , are not only determined by the intrinsic properties such as the crystalline anisotropy constant K 1 and the magnetostriction constant , but also by the microstructural parameters including grain size, texture, defects, and precipitates.…”

Magnetization reversal in bicrystal media

“…3 For two of the four samples the substrates were annealed in air at 200°C. The structure of the films is described in detail by McKinlay et al 3 The magnetic measurements were made on Princeton Measurement Systems Alternating Gradient Force Magnetometer ͑AGFM͒, with the field applied in the plane of the film and in the circumferential direction. Hysteresis loops were measured as were IRM curves following demagnetization of the samples in a 5 kOe, 50 Hz ac field DCD curves were measured from the saturated state.…”

“…2 Films with a subgrain bicrystal structure have been manufactured which are polycrystalline with their overall magnetic properties planar isotropic. 3 They consist of bicrystal clusters which contain subgrains, exhibiting two orthogonal c-axes.…”

Stacking faults and their effect on magnetocrystalline anisotropy in Co and Co-alloy thin films

“…Stacking faults in Co-alloy magnetic media have been investigated by diffraction contrast imaging [2], high-resolution transmission electron microscopy [3]- [5] and grazing incidence x-ray scattering using synchrotron radiation [6]. Although intensive research efforts have been undertaken with the purpose of improving the recording properties, the effects of stacking faults on the magnetic properties such as coercivity are still controversial due to the difficulty in quantitatively characterizing stacking fault density and separating the effects of stacking faults from other influences such as grain size, composition and orientation [4], [7]- [9]. Hence, knowledge of the effects of stacking faults on anisotropy constants is essential for the development of high density Co-alloy media.…”