title: Mapping of single-site magnetic anisotropy tensors in weakly coupled spin clusters by torque magnetometry.
abstract: Single-crystal torque magnetometry performed on weakly-coupled polynuclear systems provides access to a complete description of single-site anisotropy tensors. Variable-temperature, variable-field torque magnetometry was used to investigate triiron(III) complex [Fe3La(tea)2(dpm)6] (Fe3La), a lanthanum(III)-centred variant of tetrairon(III) single molecule magnets (Fe4) (H3tea = triethanolamine, Hdpm = dipivaloylmethane). Due to the presence of the diamagnetic lanthanoid, magnetic interactions among iron(III) ions (si = 5/2) are very weak (<0.1 cm(−1)) and the magnetic response of Fe3La is predominantly determined by single-site anisotropies. The local anisotropy tensors were found to have Di > 0 and to be quasi-axial with |Ei/Di| ~ 0.05. Their hard axes form an angle of approximately 70° with the threefold molecular axis, which therefore corresponds to an easy magnetic direction for the molecule. The resulting picture was supported by a High Frequency EPR investigation and by DFT calculations. Our study confirms that the array of peripheral iron(III) centres provides substantially noncollinear anisotropy contributions to the ground state of Fe4 complexes, which are of current interest in molecular magnetism and spintronics.
authors.affiliation: Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia & INSTM RU of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy. andrea.cornia@unimore.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Rigamonti
authors.forename: Andrea
authors.initials: A
authors.lastname: Cornia
authors.forename: Andrea
authors.initials: A
authors.lastname: Nava
authors.forename: Mauro
authors.initials: M
authors.lastname: Perfetti
authors.forename: Marie-Emmanuelle
authors.initials: ME
authors.lastname: Boulon
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Barra
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Zhong
authors.forename: Kyungwha
authors.initials: K
authors.lastname: Park
authors.forename: Roberta
authors.initials: R
authors.lastname: Sessoli