Abstrakt
Electronic properties of Dy3Ru4Al12 (hexagonal crystal structure, Dy atoms form distorted kagome nets) are studied on a single crystal by means of magnetization, neutron diffraction, specific heat, and resistivity measurements. The onset of a long-range magnetic order of Dy moments occurs at 7 K through a first-order phase transition.
The compound has a noncollinear antiferromagnetic structure with a propagation vector (1/2 0 1/2). The configuration of the Dy moments is consistent with the monoclinic Shubnikov group C(c)2/c.
The gamma coefficient in the temperature linear term of the specific heat is strongly enhanced to 500 mJ mol(-1) K-2 taking into account the localized nature of Dy magnetism. An additional contribution originates from spin fluctuations induced in the 4d subsystem of Ru by the exchange field acting from the Dy 4f moments.
In an applied magnetic field Dy3Ru4Al12 displays magnetization jumps along all crystallographic directions. All the metamagnetic transitions are accompanied by large positive magnetoresistance.
The maximum effect (125%-140%) is attained for current along the [100] axis and field along the [120] or [001] axes. The large positive effect is explained by changes in the conduction electron spectra through the jumps as the conduction electrons interact with localized magnetic moments.