title: High-temperature slow relaxation of the magnetization in Ni10 magnetic molecules.
abstract: We investigate a family of molecular crystals containing noninteracting Ni10 magnetic molecules. We find slow relaxation of the magnetization below a temperature as high as 17 K and we show that this behavior is not associated with an anisotropy energy barrier. Ni10 has a characteristic magnetic energy spectrum structured in dense bands, the lowest of which makes the crystal opaque to phonons of energy below about 1 meV. We ascribe the nonequilibrium behavior to the resulting resonant trapping of these low-energy phonons. Trapping breaks up spin relaxation paths leading to a novel kind of slow magnetic dynamics which occurs in the lack of anisotropy, magnetic interactions and quenched disorder.
authors.affiliation: Dipartimento di Fisica, Università di Parma, I-43100 Parma, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Carretta
authors.forename: P
authors.initials: P
authors.lastname: Santini
authors.forename: G
authors.initials: G
authors.lastname: Amoretti
authors.forename: M
authors.initials: M
authors.lastname: Affronte
authors.forename: A
authors.initials: A
authors.lastname: Candini
authors.forename: A
authors.initials: A
authors.lastname: Ghirri
authors.forename: I S
authors.initials: IS
authors.lastname: Tidmarsh
authors.forename: R H
authors.initials: RH
authors.lastname: Laye
authors.forename: R
authors.initials: R
authors.lastname: Shaw
authors.forename: E J L
authors.initials: EJ
authors.lastname: McInnes