Origin of the resistivity increase in gadolinium hydride halides: GdXH(D)y (X = Cl, Br, I; 0.67<y<1.0)

The electrical resistivity of GdXHy (X=Cl, Br, I; 0.67<y<1.0) undergoes a strong increase (several orders of magnitude for X=Br,I) at low temperatures (<20 K) when the hydrogen concentration y approaches its lower limit of 0.67. Here, we report on resistivity measurements on samples exposed to a special thermal treatment and in high magnetic fields. In both cases, the resistivity increase changes significantly. A slow cooling rate from 450 to 200 K favors the increase which seems to indicate that a better ordering of the H atoms enhances the resistivity at low temperatures. On the other hand, the magnetoresistivity measurements reveal that the resistivity increase can be completely suppressed by magnetic fields up to 20 T. This result emphasizes the strong connection between the electrical and the magnetic properties since the magnetic field will counteract the magnetic order. (orig.e