Study of muon magnetic hyperfine and nuclear quadrupole interactions and easy axis in the organic ferromagnet p-Cl-Ph-CHN-TEMPO

• Published in: Physica. B, Condensed matter Vol. 334; no. 3; pp. 335 - 342
• Main Authors: Jeong, Junho, Briere, Tina M., Ohira, S., Sahoo, N., Nishiyama, K., Nagamine, K., Das, T.P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-07-2003; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dipole–dipole interactions; Easy axis; Electron states; Exact sciences and technology; Hyperfine interactions; Level splitting and interactions; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Muon spin rotation and relaxation; Organic ferromagnet; Other ferromagnetic metals and alloys; Physics; Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect; Spin-orbit coupling, zeeman, stark, and strain splitting, jahn-teller effect; Studies of specific magnetic materials; Hyperfine interactions; Easy axis; Organic ferromagnet; Dipole–dipole interactions; Muon spin relaxation; Dipole dipole interaction; Inorganic compounds; Amines; Magnetic dipoles; Quadrupole interactions; Theoretical study; Ferromagnetic materials; Magnetic moments; Electronic density of states; Monoclinic lattices; Radicals; Dipole-dipole interactions; Trapping; Electronic structure; Piperidines; Chloro complex; Organic compounds
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(03)00095-4

The first-principles Hartree–Fock cluster procedure has been used for studying the electronic structure of the organic ferromagnetic p-Cl-Ph-CHN-TEMPO (4-(p-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-yloxyl) radical system with and without positive muon or muonium. Theory is able to provide quantitative information about the trapping sites for muon and muonium and the associated muon hyperfine interaction parameters. Using this information, two sites, one with muonium trapped near oxygen in the electronic singlet state of the muonium–radical pair system involved and the other with muon trapped near chlorine, are identified as likely candidates for the source of the experimentally observed μSR frequency of 3.2
MHz from zero-field measurement. The easy axis is obtained in both cases as the
b-axis in the monoclinic lattice in agreement with the results of our magnetic dipole–dipole interaction studies using the magnetic moment distributions in the ferromagnetic state in the absence of muon and muonium. Nuclear quadrupole interaction parameters for nuclei adjacent to the trapped muon and muonium have been evaluated and their role in distinguishing between alternate trapping sites is discussed.