Realization of an N -shaped Iv C of Nanoscale Metallic Junctions Using the Antiferromagnetic Transition

We have observed at low temperatures (≤ 8K) hysteretic I(V ) characteristics for sub-μm (∼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 ρ(T ) of UPd2Al3 near the Néel temperature TN ≃ 14K. From this point of view each metal with similar ρ(T ) should produce similar hysteretic I(V ) curves. 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 1 ns for the investigated contacts.