Tunneling experiments involving magnetic tip and magnetic sample

Preliminary STM experiments have been performed on a Fe polycrystal using a CoCr magnetic tip. With the usualW-tip, the Fe topography reveals a typical polycrystalline corrugation. The CoCr tip was obtained by cleaving a Si wafer covered with a CoCr film. Its operation was verified to be normal on a Cu single-crystal surface. The combination of Fe sample and CoCr tip leads to a strongly enhanced corrugation as compared to the normal topography. A preliminary explanation, in terms of force enhancement, is based on the interaction of the tip magnetic moment with the field gradient near the sample surface.