The magnetocrystalline anisotropy properties of rare earth-transition metal single crystals and thin films.

摘要

Rare earth-transition metal magnet materials form the basis of high energy bulk and thin film permanent magnets which have desirable intrinsic properties (Curie temperature T{dollar}rm sb{lcub}c{rcub}{dollar}, saturation magnetization M{dollar}rm sb{lcub}s{rcub}{dollar}, and anisotropy field H{dollar}rm sb{lcub}a{rcub}{dollar}) needed for practical applications. This study focused on the intrinsic properties of two iron-rich classes of rare earth-transition metal materials, and on Sm-Co type thin film magnets which have applications where the use of bulk magnets is not optimal, as in defense and space applications where weight and size constraints exist.; Research efforts focused on iron-rich, ThMn{dollar}sb{lcub}12{rcub}{dollar}-type crystal samples across the NdFe{dollar}rm sb{lcub}10-x{rcub}{dollar}Co{dollar}sb{lcub}x{rcub}{dollar}Mo{dollar}sb2{dollar} series and a new iron-rich {dollar}rm Rsb3(Fe,M)sb{lcub}29{rcub}{dollar} series which was discovered by a group at the General Motors Company. Single crystals of {dollar}rm NdFesb{lcub}10-x{rcub}Cosb{lcub}x{rcub}Mosb2{dollar} with x {dollar}epsilon{dollar} {dollar}{lcub}0, 1, 3, 5, 7, 10{rcub},{dollar} and {dollar}rm Rsb3Fesb{lcub}29-x{rcub}Tisb{lcub}x{rcub}{dollar} with R {dollar}epsilon {lcub}rm Ce, Nd, Pr{rcub}{dollar} and x = 1.5 were grown by the Czochralski technique using a tri-arc furnace. Only polycrystalline samples had been available previously; single crystals are better defined and characterized and for that reason are expected to give more accurate information about the magneto-crystalline anisotropy of these magnetic alloys. Temperature-induced spin reorientations were observed in {dollar}rm NdFesb{lcub}10-x{rcub}Cosb{lcub}x{rcub}Mosb2{dollar} for x {dollar}<{dollar} 5 as were field-induced spin reorientations for x {dollar}ge{dollar} 3, restricting their use for permanent magnet applications. Magnetic anisotropy in {dollar}rm NdFesb{lcub}10-x{rcub}Cosb{lcub}x{rcub}Mosb2{dollar} was augmented by Co addition, but the anisotropy seen in {dollar}rm Rsb3Fesb{lcub}29-x{rcub}Tisb{lcub}x{rcub}{dollar} was quite low for permanent magnet applications.; Aligned {dollar}rm Smsb2Cosb{lcub}17{rcub}{dollar} films usually require subsequent annealing for optimum results. Growth of in-plane aligned hard magnetic films without need for subsequent processing is desirable for device applications so composite SmCo{dollar}sb5{dollar} and Sm(Co,Fe,Cu,Zr){dollar}sb7{dollar} thin films were grown on {dollar}rm Alsb2Osb3{dollar}, MgO (100), Si (100), AlN, and c-plane (001) sapphire substrates to investigate their magnetic and structural properties. RF magnetron sputtering was used to deposit the films. Films grown on {dollar}rm Alsb2Osb3{dollar} and Si (100) had crystallites largely in plane as seen in X-ray measurements, magnetic hysteresis loops measured in two directions, and electron microscopy. The films grown on MgO (100), AlN, and sapphire were also oriented in-plane with a small fraction of crystallites aligned out-of-plane. For films with square loops (a high volume fraction of hard magnetic phases), intrinsic coercivity was greater than 10 kOe, remanent magnetization was 6-7 kG, maximum energy products were as high as 10 MGOe, and post-deposition annealing was not required.