Magnetism and giant magnetoresistance of YMn6Sn6-xGax (x=0-1.8) compounds - art. no. 212404

Magnetic and transport properties of YMn6Sn6-xGax(0 less than or equal tox less than or equal to1.8) compounds with the HfFe6Ge6-type structure were i nvestigated. It was found that Ga substitution leads to a contraction of th e unit-cell volume. A transition from an antiferromagnetic to a ferromagnet ic (or ferrimagnetic) state can be observed for 0.1 less than or equal tox less than or equal to0.2 with increasing temperature. The antiferro-ferroma gnetic transition for samples with x less than or equal to0.2 can also be i nduced by an external field. The metamagnetic transition field is very low, and decreases with increasing Ga concentration, Higher Ga concentration (x >0.2) leads to the samples being ferromagnetic in the whole temperature ran ge below the Curie temperature. Ga substitution weakens the interlayer magn etic coupling between the Mn spins. Corresponding to the metamagnetic trans ition, a magnetoresistance as large as 32% in a field of 5 T was observed a t 5 K for the sample with x=0.2. Results from the Sn-119 Mossbauer spectra indicate that the Mn-Mn coupling through the "Mn-Sn-Sn-Mn" slab change from antiferromagnetic in YMn6Sn6 to ferromagnetic by the substitution of Ga fo r Sn.