Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films

The composition dependence of the structural, magnetic, and transport properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal structure was observed to change from tetragonal to cubic as the Co content was increased. In terms of the dependence of saturation magnetization on the Co content, relatively small value was obtained for the Mn$_{2.3}$Co$_{0.4}$Ga$_{1.3}$ film at a large {\it K}$_\textrm u$ value of 9.2 Merg/cm$^3$. Electrical resistivity of Mn-Co-Ga films was larger than that of pure Mn-Ga film. The maximum value of the resistivity was 490 $\mu\Omega$cm for Mn$_{2.2}$Co$_{0.6}$Ga$_{1.2}$ film. The high resistivity of Mn-Co-Ga might be due to the presence of localized electron states in the films due to chemical disordering caused by the Co substitution.Comment: 3 pages, 5 figures. The article has been submitted to the Journal of Applied Physics as a Proceedings for the 12th Joint MMM/INTERMAG conferenc

Perpendicularly magnetized Mn-Co-Ga-based thin films with high coercive field

Mn$_{3-x}$Co$_{x}$Ga epitaxial thin films were grown on MgO substrates by magnetron co-sputtering. Structures were tetragonal or cubic depending on Co content. Composition dependence of saturation magnetization and uniaxial magnetic anisotropy $K_u$ of the films were investigated. A high $K_u$ (1.2 MJ m$^{-3}$) was achieved for the Mn$_{2.6}$Co$_{0.3}$Ga$_{1.1}$ film with the magnetic moment 0.84$\mu_B$. Valence band spectra were obtained by hard X-ray photoelectron spectroscopy. Sharp peaks in the cubic case, which were absent in the tetragonal case, prove that a van Hove singularity causes a band Jahn-Teller effect with tetragonal distortion. Observations agree well with the first-principles calculations

Fabrication of high-magnetoresistance tunnel junctions using Co75Fe25 ferromagnetic electrodes

科研費報告書収録論文(課題番号:11355001・基盤研究(A)(2)・H11～H13/研究代表者:宮崎, 照宣/ﾊｲﾌﾞﾘｯﾄﾞ磁性体の微細化ﾌﾟﾛｾｽとﾄﾝﾈﾙ再生磁気ﾍｯﾄﾞの作製

INSTABILITY OF PERMEABILITY OF AN AMORPHOUS Fe_5Co_<70>Si_<15>B_<10> ALLOY

Exciting field (0～250 mOe) and temperature (-196～420℃) dependences of permeability and disaccommodation have been studied for a rapidly quenched amorphous Fe_5Co_Si_B_ alloy by using an automatic measuring apparatus of disaccommodation. Disaccommodation takes a broad maximum of about 6% at around room temperature and also a broad and large maximum, 10～30%, at about 190℃ after cooling from 420℃, which is below the crystallization temperature. The former and later maximum points correspond roughly to the Curie points of Co_2B and (Fe-Co)_2 B alloys, respectively, which are the constitutional alloys of a crystallized Fe_5Co_Si_B_ alloy

Electron transport properties in magnetic tunnel junctions with epitaxial NiFe (111) ferromagnetic bottom electrodes

科研費報告書収録論文(課題番号:13305001・基盤研究(A)(2) ・H13～H15/研究代表者:宮崎, 照宣/高品位微小トンネル接合へのスピン注入