Development of novel magnetic materials is of interest for fundamental studies and applications such as spintronics, permanent magnetics, and sensors. We report on the first experimental realization of single element ferromagnetism, since Fe, Co, and Ni, in metastable tetragonal Ru, which has been predicted. Body-centered tetragonal Ru phase is realized by use of strain via seed layer engineering. X-ray diffraction and electron microscopy confirm the epitaxial mechanism to obtain tetragonal phase Ru. We observed a saturation magnetization of 148 and 160 emu cm-3 at room temperature and 10 K, respectively. Control samples ensure the ferromagnetism we report on is from tetragonal Ru and not from magnetic contamination. The effect of thickness on the magnetic properties is also studied, and it is observed that increasing thickness results in strain relaxation, and thus diluting the magnetization. Anomalous Hall measurements are used to confirm its ferromagnetic behavior.
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The authors would like to thank Drs. Ramamoorthy Ramesh from UC Berkeley, Weigang Wang from Arizona State University, Delin Zhang from the University of Minnesota, and Julie Borchers, Michelle Jamer, and Brian Kirby from NIST for invaluable discussion. This work was supported by C-SPIN, one of six STARnet program research centers, and by the University of Minnesota Distinguished Doctoral Fellowship. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program, and the Materials Science Center, University of Wisconsin-Madison, which is supported by the NSF MRSEC program (DMR-1720415).
Materials Science Center, University of Wisconsin-Madison, which is supported by the NSF MRSEC program (DMR-1720415).