Electrochemical Preparation And Magnetic Properties Of CoPtMo Magnetic Thin Films

CoPt alloy films possess high coercivity, great magnetic anisotropyconstant and optimal oxidation resistance which could be used in the field ofmicro-electromechanical systems devices, membrane heads, card readers and datastorage media. In recent years, using electrochemical deposition method to prepareCoPt magnetic films has been carried out in many countries and achieved manyresults. It was found out that, CoPt alloy films with20%Pt contents could possesshigher coercivity without higher temperature annealing process. However, cost ofCoPt alloy films is expensive. Compare to CoPt alloy films, CoPtW films obtainedby doping W element also have great coercivity. Elements Mo and W have similarchemical properties, so that they could be codeposited with Cobalt which is seldomreported. Effects of deposition parameters on structures, components, surfacemorphology and magnetic properties of CoPtMo alloy films were investigated in thepaper. The research of the paper mainly includes the following three aspects:(1) CoPtMo alloy films were obtained by electroless plating technology from analkaline solution. Influences of pH values and molybdenum salt concentrations onproperty of films were studied. With the increase of pH values, deposition rate and Ptcontents of films increased gradually. However, coecivity first increased and thendecreased with the rise on pH values. In addition, Pt contents in the films decreasedgradually with the rise on molybdenum salt concentrations. Higher concentration ofmolybdenum salt could affect the surface morphology of films to form poroussurface. CoPtMo alloy films with coercivity (290KA/m) and components (87%Co,7.9%Pt) could be obtained in the condition of pH=12.5and0.005mol/Lmolybdenum salts.(2) CoPtMo thin films were prepared by electrodeposition method. Effects ofdifferent pH values, hypophosphite concentrations on structures, composition,morphology and magnetic property of films were investigated. It was found that,although P element was less in the films, P element would play an extremelyimportant role in coercivity of films. CoPtMo films with fcc structure could be obtained without hypophosphite. With the increase of pH values, cobalt contents inthe films increased while Pt contents declined. Higher pH values could induce toobtain films with smaller particles and smooth surface. However, films prepared inthe condition of higher pH values possessed lower coercivity (24.1KA/m).Reduction potential became negative with higher hypophosphite concentrations,which could increase cobalt contents and affect surface morphology of CoPtMo films.CoPtMo alloy films with coercivity (136KA/m) and components (76.1%Co,12%Pt)could be obtained in the condition of pH=10and0.0075mol/L molybdenum salts.(3) CoPtMo alloy films were prepared by magnetic electrodeposition methods.Influences of various magnetic intensities on surface morphology, structures,components and magnetic performance of films were studied. Lorentz forcegenerated during magnetic deposition process could smooth surface and decreaseparticle size. With the magnetic field ranged from0to0.7T, component of CoPtMowas stable. However, coercivity of films increased first and then decreased with therise on magnetic intensity. Fimes with maximum coercivity (159KA/m) could beobtained in the condition of0.4T.