Realization of an N-Shaped IVC of Nanoscale Metallic Junctions Using the Antiferromagnetic Transition

We have observed at low temperatures (< 8 K) hysteretic I(V) characteristics for sub-pin (similar to 200 nm) metallic break-junctions based on the heavy-fermion compound UPd2Al3. Degrading the quality of the contacts by in situ increasing the local residual resistivity or temperature rise reduces the hysteresis. We demonstrate that those hysteretic I(V) curves can be reproduced theoretically by assuming the constriction to be in the thermal regime. Our calculations show that such anomalous I(V) curves are due to the sharp increase of p(T) of UPd2Al3 near the Neel temperature T-N approximate to 14 K. From this point of view each metal with similar p(T) should produce similar hysteretic I(V) characteristics. As example we show calculations for the rare-earth manganite La0.75Sr0.25MnO3, a system with colossal magnetoresistance. In this way we demonstrate that nano-sized point contacts can be non-linear devices with N-shaped I(V) characteristics, i.e. with negative differential resistance, that could serve like Esaki tunnel diodes or Gunn diodes as amplifiers, generators, and switching units. Their characteristic response time is estimated to be less than Ins for the investigated contacts.