Anisotropic Curie temperature materials. Issue 2 (23rd October 2012)

• Record Type: Journal Article
• Authors: Armstrong, Jason N.; Hua, Susan Z.; Chopra, Harsh Deep
• Is Part Of: Physica status solidi. Volume 250:Issue 2(2013:Feb.)
• Page Start: 387
• Page End: 395
• Publication Date: 2012-10-23
• Subjects: Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.201248186
• Languages: English
• ISSNs: 0370-1972

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Existence of anisotropic Curie temperature materials [E. R. Callen, Phys. Rev. <bold>124</bold>, 1373 (1961); J. Appl. Phys. <bold>32</bold>, S221 (1961)] is a longstanding prediction – materials that become paramagnetic at a lower temperature along certain crystal directions while remaining magnetically ordered in other directions up to a higher temperature. Validating Callen's theory, we show that all directions within the basal plane of monoclinic Fe<sub>7</sub>S<sub>8</sub> (pyrrhotite) single crystal remain ordered up to 603 K while the <italic>c</italic>‐axis becomes paramagnetic at 225 K. Results prompt a re‐evaluation of existing magnetic materials with a focus on magnetic characteristics along different crystal orientations <italic>above</italic> instead of below the ordering temperatures. Theoretical guidelines for identifying new materials with large anisotropy of Curie temperature are also given, and analysis protocol to characterize them in a self‐consistent manner is discussed. Materials with such a large directional dependence of Curie temperature open the possibility for uniquely new devices and phenomena, including (spin) transport. <boxed-text content-type="graphic" position="anchor" orientation="portrait"><graphic position="anchor" mimetype="image" xlink:href="ark:/27927/pgg1rw4krrz" orientation="portrait" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></boxed-text></p> <p>Anisotropic Curie temperature in pyrrhotite (Fe<sub>7</sub>S<sub>8</sub>). Notice the large difference in ordering temperature along basal plane (main graph) relative to the <italic>c</italic>‐axis (inset).</p> </abstract>