B. Ramamurthy Acharya

SPUTTER DEPOSITED STRONTIUM FERRITE FILMS WITH C-AXIS ORIENTED NORMAL TO THE FILM PLANE

M‐type strontium ferrite films were deposited by radio‐frequency (rf) sputtering on fused quartz substrates kept at ambient temperatures. The as‐deposited films were amorphous. They crystallized on annealing at a temperature of 800 °C or higher. The films deposited at low rf power and low oxygen to argon ratio showed c‐axis orientation normal to the film plane. The magnetic properties of these films were studied using vibrating sample magnetometer, polar Kerr rotation, and torque magnetometer. The perpendicular M‐H loops for c‐axis oriented films were nearly rectangular with coercivity of the order of 3 kOe.

Preparation and magnetic properties of strontium ferrite thin films

Strontium ferrite films were deposited by RF sputtering of a commercial strontium ferrite target onto fused quartz substrates maintained at temperatures up to 900 degrees C. Films deposited at T 800 degrees C had crystalline M-type strontium ferrite structures. The thin composition corresponded to that of the target. Films deposited at 800 degrees C were partially oriented in the [110] direction with the c-axis in the plane. Postannealing led to an increase in the magnetization, indicating incomplete formation of ferrite in the as-deposited state. Both in-plane and perpendicular hysteresis loops are rectangular with remanence ratios of 0.8 and 0.6, respectively, showing partial orientation with the c-axis. The torque curve is consistent with the above, although there are some additional anomalous peaks. >

Ferromagnetic-resonance studies of exchange-coupled FE/NI multilayers

Abstract Multilayers of Fe/Ni have been deposited onto water-cooled glass substrates by a dc triode under computer-controlled conditions. The layer thickness was in the range 20 to 200 A and the total thickness about 600 A. FMR was observed at 9.8 GHz. The perpendicular spectra consisted of more than one mode. We have calculated the field positions of the modes and compared them with the experimental data and found that the latter were smaller by about 10%. In order to obtain a good agreement it is necessary to suppose the presence of an alloy layer about 20 A thick at each interface with an average magnetization on the order of 13 kG.

Mossbauer study of interface mixing in FE/NI multilayers

Abstract Conversion Electron Mossbauer Spectroscopy (CEMS) studies were carried out on as deposited and annealed Fe Ni multilayers prepared by rf sputtering, in order to probe the interface. A series of multilayers in which Ni layer thickness was fixed at 25 A and the Fe layer thickness was varied from 18 to 120 A, were studied. The width of the Mossbauer lines increases with decreasing Fe layer thickness indicating a mixing at the interface, which was analyzed using specific models.

Oriented strontium ferrite films sputtered onto Si(111)

Abstract Recently we have shown that M-type Sr ferrite films (SrM) can be sputter deposited on fused amorphous quartz substrates with c -axis normal to the film plane [1]. In the present study we show that the c -axis orientation of SrM on Si(111) can be tailored to vary from in plane to normal to the film plane by changing the deposition parameters.

Magnetic and FMR studies in amorphous Co80Nb10Zr10 films

Abstract Amorphous Co 80 Nb 10 Zr 10 films have been prepared by rf sputter deposition on water cooled glass substrates and their magnetic and FMR properties have been studied. The in-plane M-H loops of the as prepared films show the presence of an uniaxial anisotropy which could be annealed out by magnetic annealing. The FMR spectra with the field perpendicular to the film plane show standing spin waves but indicate some inhomogeneities. The inhomogeneities are traced to the preferential oxidation of Zr. When samples are protected in situ with a silver layer are found to be very homogeneous.

Conversion electron Mossbauer studies on strontium ferrite films with in-plane and perpendicular anisotropies

Hexagonal strontium ferrite thin films with in-plane and perpendicular magnetic anisotropies have been studied using conversion electron Mossbauer spectroscopy. The hyperfine parameters of the films were found to be similar to the one obtained for bulk strontium ferrite. However, the intensity ratios of the first and second lines of the Mossbauer spectra were found to be different for films deposited at different rf powers. This indicated a change in the anisotropy of the deposited film. The resultant change in the magnetization direction and crystallization texture was compared to other measurements.

The effect of (TbFe) thickness on the resistivity and magnetoresistance of (TbFe)/Pt multilayers

Electrical resistivity and magnetoresistance measurements were carried out, in the temperature range of 4.2K to 300K and fields up to 45 kOe on sputtered deposited (TbFe/Pt) multilayers. The Pt layer thickness was 20 A and that of TbFe layer was varied from 50 to 206 A. The properties show a large dependence on TbFe layer thickness.