Effects of localization on the magnetic transition of thin gadolinium wires

Abstract

Thin wires of gadolinium have been fabricated through a step lithographic technique with cross-sectional areas from 1.3×10−11 to 58×10−11 cm2. The Gd thin films were deposited in a UHV system by thermal evaporation and have a room-temperature resistivity of 85 μΩ cm. The electrical resistance of thin films and wires was measured by the four-probe method in the temperature range from 1.5 to 300 K. We also studied the isothermal magnetoresistance at temperatures below 30 K in a magnetic field up to 5.5 T. As the temperature decreases, the resistivity ρ of Gd wires first decreases towards a minimum at ∼55 K, then rises to a maximum at ∼ 31 K, followed by a sharp drop below 31 K. The minimum in the resistivity at 55 K is associated with the localization effect. It is believed that the sharp drop in ρ below 31 K is due to a magnetic transition in the Gd wire. This magnetic transition is possible due to a large shift in the Curie temperature caused by a reduction in the density of conduction electrons, arising from localization effects in the thin wire. The magnetoresistance (MR) data below 20 K show a negative value, and the field dependence of MR is similar to that of ferromagnetic metals. This is the first study of thin magnetic wires, to our knowledge.