Magnetization steps and bound magnetic polarons in diluted magnetic semiconductors

Magnetization measurements and computer simulations were used to address several current problems in the area of the Diluted Magnetic Semiconductors (DMS). The method of Magnetization Steps (MSTs) was used to study Jahn-Teller Distortions in {dollar}rm Znsb{lcub}1-x{rcub}Crsb{lcub}x{rcub}Te{dollar}, and exchange constants in {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Se{dollar} and {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Te{dollar}. Bound magnetic polarons in {dollar}rm Cusb2Mnsb{lcub}x{rcub}Znsb{lcub}1-x{rcub}SnSsb4{dollar} were studied by conventional magnetometry.; Jahn-Teller Distortions in cubic {dollar}rm Znsb{lcub}1-x{rcub}Crsb{lcub}x{rcub}Te{dollar} were studied using MSTs. Possible Jahn-Teller Distortions in this material are along the three equivalent {dollar}langle 100rangle{dollar} axes. Energy states for the three distortion directions are equivalent at H = 0, but are different for finite H. The main issue is whether the populations of three possible distortions will vary with field, or remain frozen at their values in zero-field. The data showed that the populations of the distortions changed significantly.; The dominant antiferomagnetic exchange constants J between Eu{dollar}sp{lcub}2+{rcub}{dollar} ions in IV-VI {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Se{dollar} and {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Te{dollar} were determined using the MST method. Measurements were made at 0.6 K in fields up to 150 kOe. Supplementary data by our collaborators were taken at much lower temperatures. Simulations of various MSTs (from isolated Eu{dollar}sp{lcub}2+{rcub}{dollar} ions, pairs of ions, and triplets) were performed to fit the experimental data. Because J is determined from the MSTs for pairs, the effects of other anisotropies and exchange interactions on these MSTs were considered. They were found to bring little change to the values of J. The exchange constants were {dollar}J/ksb{lcub}B{rcub}{dollar} = {dollar}-{dollar}0/24 {dollar}pm{dollar} 0.03 K for Ph{dollar}sb{lcub}rm 1-x{rcub}{dollar}Eu{dollar}sb{lcub}rm x{rcub}{dollar}Se amd os {dollar}J/Ksb{lcub}B{rcub}{dollar} = {dollar}-{dollar}0.264 {dollar}pm{dollar} 0.018 K for {dollar}rm Phsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Te{dollar}. The dominant AF exchange constants were identified as J{dollar}sb1{dollar}, between nearest-neighbors, by comparing the experimental magnetization curves to the theoretical simulations using the single J model.; The dominant antiferromagnetic exchange constants J between Eu{dollar}sp{lcub}2+{rcub}{dollar} ions in IV-VI {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Se{dollar} and {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Te{dollar} were determined using the MST method. Measurements were made at 0.6 K in fields up to 150 kOe. Supplementary data by our collaborators were taken at much lower temperatures. Simulations of various MSTs (from isolated Eu{dollar}sp{lcub}2+{rcub}{dollar} ions, pairs of ions, and triplets) were performed to fit the experimental data. Because J is determined from the MSTs for pairs, the effects of other anisotropies and exchange interactions on these MSTs were considered. They were found to bring little change to the values of J. The exchange constants were {dollar}J/ksb{lcub}B{rcub}{dollar} = {dollar}-{dollar}0.24 {dollar}pm{dollar} 0.03 K for {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Se{dollar} and is {dollar}J/ksb{lcub}B{rcub}{dollar} = {dollar}-{dollar}0.264 {dollar}pm{dollar} 0.018 K for {dollar}rm Pbsb{lcub}1-x{rcub}Eusb{lcub}x{rcub}Te{dollar}. The dominant AF exchange constants were identified as J{dollar}sb1{dollar}, between nearest-neighbors, by comparing the experimental magnetization curves to the theoretical simulations using the single J model.; Bound Magnetic Polarons (BMP) in p-type {dollar}rm Cusb2Mnsb{lcub}x{rcub}Znsb{lcub}1-x{rcub}SnSsb4{dollar} samples were studied. Magnetization measurements wer...