title: Magnetisation inverted hysteresis loops in the molecular magnets [M(Cp)2][Ni(alpha-tpdt)2] (M = Fe, Mn).
abstract: The low temperature magnetic properties of the compounds belonging to the family [M(Cp)(2)][Ni(alpha-tpdt)(2)], where M = Fe (), Mn () and Cr () (alpha-tpdt = 2,3-thiophenedithiolate) are studied, with emphasis on the magnetisation curves. These compounds share a common structure, composed of alternating layers, each consisting of mixed parallel D(+)A(-)D(+)A(-)D(+)A(-) chains; the chains of adjacent layers being perpendicular. At low temperatures, a rather unusual inverted hysteresis loop with negative remanence is observed in 1, and a similar reversed hysteresis is also detected in the magnetic field induced transition of 2. This effect is associated with the layered structure of these compounds, together with the considerable magnetic anisotropy of the [Fe(Cp)(2)](+) and [Mn(Cp)(2)](+) donors, being to the best of our knowledge, the first time such inverted hysteresis loops are observed in a bulk molecule based material.
authors.affiliation: Departamento de Química, Instituto Tecnológico e Nuclear/CFMCUL Estrada Nacional 10, P-2686-953, Sacavém, Portugal.
authors.forename: Dulce
authors.initials: D
authors.lastname: Belo
authors.forename: Laura Cristina
authors.initials: LC
authors.lastname: Jesus Pereira
authors.forename: Manuel
authors.initials: M
authors.lastname: Almeida
authors.forename: Concepció
authors.initials: C
authors.lastname: Rovira
authors.forename: Jaume
authors.initials: J
authors.lastname: Veciana
authors.forename: Vasco
authors.initials: V
authors.lastname: Gama