K. Nishioka

Magnetic properties of sputtered Co-Ni-Fe-Pd films for thin-film heads

Magnetic properties of Co-Ni-Fe-M (M=Rh, Ir, Pd, Pt) films prepared by sputtering are investigated. It is found that addition of Pd decreases the magnetostriction constant of the films from 1*10/sup -5/ to around zero. On the other hand, addition of other elements, such as Rh, Ir, and Pt, increases it. However, coercive forces of Co-Ni-Fe-Pd films become more than 10 Oe when the magnetostriction is less than 2*10/sup -6/. Multilayered films are investigated to obtain films with low coercive force. 43Co-27Ni-15Fe-15Pd films of 0.17 mu m and Al/sub 2/O/sub 3/ films of 0.01 mu m in thickness are layered time-sequentially. This multilayered film has saturation induction of 1.4 T, approximately=0 magnetostriction, and a low coercive force of 1.5 Oe. Furthermore, Co-Ni-Fe-Pd films are ascertained to be as resistant to corrosion as Permalloy films. Recording heads with multilayered Co-Ni-Fe-Pd films with Al/sub 2/O/sub 3/ interlayers as magnetic cores have been fabricated. Recording characteristics were evaluated. These laminated Co-Ni-Fe-Pd/Al/sub 2/O/sub 3/ heads exhibit about 6 dB better overwrite than Permalloy heads. >

Domain structures in multi-layered Co-Ni-Fe-Pd films observed by spin-polarized SEM

The domain structures of cores with patterned six-layered CoNiFePd films with alumina interlayers are investigated using spin-polarized scanning electron microscopy. The films exhibit virtually single domains in the middle of the magnetic cores with magnetization parallel to the easy axis of the films. Around the pattern edge, the magnetization orients along the pattern edge. At the pole tip, the ratio of the edge domain to the pole width increases as the track width becomes narrow. It is important to prevent the enlargement of such a region so as to maintain the permeability at the pole tip. This domain structure remains stable for different magnetization conditions, a necessary condition for readout waveforms without distortions. Thus the films are suitable for magnetic thin-film heads with narrow track widths. >

Study on behaviors of pinned layer by high field transfer curve

A synthetic-pinned GMR sensor is prepared by sputtering method and is lapped until its resistance reaches approximately R = 40/spl Omega/. The behaviour of the pinned layer is investigated by measuring the transfer curve change using a high-field quasi-tester. No change is observed at minor curve, whereas major curve shows completely different results, thus it is clear that introduction of high field quasi test combined with low field quasi test provides in-depth information on overall performance of the GMR sensor. Based on actual measurement of the transfer curve, several models are employed for the interpretation of each case, especially from the viewpoint of behavior of pinned layer exchange coupled by antiferromagnetic layer.

Ferro-Antiferromagnftic Coupling (2); Analysis of Experimental Results

309 H =-f J I i H , , ex a M , t , D where f, is the structural parameter of order of unity. J , is the microscopic exchange coupling energy, M , is the saturation magnetization, t, is the thickness of Fe lRNisl , and D is the antiferromagnetic grain size. The first term is the averaged exchange field at the interface of all the grains deduced from random field approximation. The inclination of the line gives the microscopic exchange-coupling energy J , of, which is reasonable order of magnitude. The second term H , is a contribution from the intergrain couplings. This contribution H , is negative when the buffer layer thickness is in the range from 0 to 20 nm. whereas the value of H , is positive when the buffer layer thickness is in the range from 50 to 100 nm. This indicates that the antiferromagnetic grain growth associated with an increase of the buffer layer thickness suppresses the aniferromagnetic domain wall propagation during the magnetization reversal. On the contrary. when the buffer layer is thin, the antiferromagnetic grains seem to be weakly coupled through grain boundaries, and this encourages the antiferromagnetic domain wall propagation.

Evaluation of Magnetization Process in Thin Film Head by Spin-Polarized SEM

The magnetic domain structures of NiFe films in thin film heads driven by dc and ac currents were investigated using spin-polarized SEM, in order to study the magnetization process under high-frequency magnetic fields. The image contrast under a high-frequency magnetic field was calculated as the time-averaged component of the magnetization along the detection direction due to magnetization rotation and to reversible domain wall movement. From the relation between the observed domain images and the calculated distribution of the average magnetization about the domain wall, it was found that irreversible domain wall movement occurs throughout the magnetic core under high-frequency excitations. Domain walls move slightly and reversibly until the direction of the magnetic field is reversed under high-frequency excitation.