Temperature effects in barium ferrite particles

Barium ferrite particulate media have attracted considerable interest for high density magnetic recording applications because they can be oriented to provide a perpendicular easy axis of magnetization and they can be mass-produced with existing coating facilities. Their perpendicular magnetization endows them with excellent short wavelenght response, but at the same time tends to highlight writing field deficiencies, because the perpendicular component of the writing head field is considerably smaller than the horizontal head field component. The situation is further aggravated by the employment of very narrow gap ring heads, dictated by the need to provide a sharp writing field gradient and to avoid read gap losses. When you consider these potential limitations, the first casualty we are likely to encounter is overwrite performance, particularly in interchangeable media applications. If, in addition to the above, we also have some temperature variation of the magnetic parameters, then temperature dependence of overwrite modulation could become unacceptable. In this study, we measured the temperature coefficients of the magnetic parameters of many different Ba-ferrite particles and coatings. We found very large differences among the various particles which can be explained on the basis of a simple theoretical model. We conclude that it is necessary and possible to make a Judicious choice of particle characteristics in order to avoid any potential temperature-related problems in recording applications.