Magnetic transition in highly frustrated SrCr8Ga4O19: The archetypal kagomé system

Both dc and ac magnetic susceptibility have been carefully measured and analyzed in order to determine the features of the low-temperature magnetic state of the highly frustrated SrCr 8 Ga 4 O 19 compound. The scaling analysis of the nonlinear part of the dc magnetic susceptibility gives clues that indicate that the nature of the magnetic state below T f does not correspond to a conventional spin glass. This idea is further confirmed by the study of the dynamic scaling that also differs from what is expected for a conventional spin glass. A progressive change towards a more conventional magnetic ordering below T f is observed by substituting Ga atoms by Fe atoms in the compound SrCr 8 Ga 4 − 2 x Fe x O 19 . For x=1.5, both the scaling analysis of the nonlinear part of the dc magnetic susceptibility and the dynamic scaling seem to indicate that a true spin-glass phase transition does exist at T f . This change in the magnetic behavior is attributed to the fact that the presence of a magnetic atom in the 4 f VI sites as a first neighbor of the Cr atoms, located in the 12k sites, will impose a ‘‘local preferential direction’’ for the magnetic moments removing somehow the strong intrinsic magnetic frustration of the kagomé lattice