Effects of stoichiometry on the magnetic and structural properties of perpendicular barium ferrite thin film media
The effects of stoichiometry factor n on the magnetic and structural properties of perpendicular barium ferrite thin films with composition of BaO.n(Fe/sub 2/O/sub 3/) were systematically investigated. Within the range 2.2<n<6, the c-axis for barium ferrite thin films can be oriented perpendicularly by the use of a Pt underlayer and with optimized processing conditions. Perpendicular c-axis orientation becomes worse as n decreases from 6 to 2.2. The average grain size was greatly reduced from about 2000 /spl Aring/ to 300 /spl Aring/ with the decrease of n. The decrease of the grain size can be related to the existence of nonmagnetic phase BaFe/sub 2/O/sub 4/, which was observed by X-ray diffraction.
Influences of sputtering gas pressure on microtexture and crystallographic characteristics of Ba-ferrite thin films for high density recording media
Ba-ferrite films with small c-axis dispersion angle Δθ 50 are suitable for ultrahigh density recording media. The dependences of partial oxygen gas pressure P O2 and total discharge gas pressure P Total on the characteristics of Ba-ferrite films were clarified. It was found that there were three regions, where films were composed of single layer of spinel type ferrite(P O2 ≤0.002mTorr), mixed layer of spinel and magnetoplumbite type ferrites ( 0.003 \leq P_{O2} \leq 0.2 mTorr) and single layer of magnetoplumbite type ferrite (P O2 >0.3 mTorr). In the range of P 02 between 0.005 and 0.2 mTorr, spinel-like ferrite layer plays very important role as an underlayer to decrease the Δθ 50 of the Ba-ferrite layer. Films deposited at relatively low P O2 and P Total exhibit very smooth surface and Δθ 50 as small as 2.5\sim3.5\deg .
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.