We show that the superconductivity observed recently in the weak itinerant ferromagnet ZrZn2 [ C. Pfleiderer et al. Nature (London) 412 58 (2001)] is due to remnants of a superconducting layer induced by spark erosion. Results of resistivity, susceptibility, specific heat, and surface analysis measurements on high-quality ZrZn2 crystals show that cutting by spark erosion leaves a superconducting surface layer. The resistive superconducting transition is destroyed by chemically etching a layer of 5 μm from the sample. No signature of superconductivity is observed in ρ(T) of etched samples at the lowest current density measured, J=675 A m−2, and at T⩾45 mK. Energy-dispersive x-ray analysis shows that spark-eroded surfaces are strongly Zn depleted. The simplest explanation of our results is that the superconductivity results from an alloy with higher Zr content than ZrZn2.
Superconductivity induced by spark erosion in ZrZn2
Shanker Saxena, Siddharth;
2005-01-01
Abstract
We show that the superconductivity observed recently in the weak itinerant ferromagnet ZrZn2 [ C. Pfleiderer et al. Nature (London) 412 58 (2001)] is due to remnants of a superconducting layer induced by spark erosion. Results of resistivity, susceptibility, specific heat, and surface analysis measurements on high-quality ZrZn2 crystals show that cutting by spark erosion leaves a superconducting surface layer. The resistive superconducting transition is destroyed by chemically etching a layer of 5 μm from the sample. No signature of superconductivity is observed in ρ(T) of etched samples at the lowest current density measured, J=675 A m−2, and at T⩾45 mK. Energy-dispersive x-ray analysis shows that spark-eroded surfaces are strongly Zn depleted. The simplest explanation of our results is that the superconductivity results from an alloy with higher Zr content than ZrZn2.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
