Figure 4

Resistivity versus temperature curves and resistivity vs. magnetic field curves. (a) Resistivity versus temperature (R-T) curves for the LPCMO wires under a 3.75-T magnetic field[27]. Arrows indicate the direction of the temperature ramp. The R-T curves all exhibit hysteresis behavior in cooling-warming cycles, which is consistent with the coexistence of ferromagnetic metal and charge-ordered insulator domains in the LPCMO system. The MIT is rather smooth for both the 20-μm and the 5-μm wires. Ultrasharp and giant steps are clearly visible for the 1.6-μm wire. (b) Resistivity vs. magnetic field curves for the LPCMO wires measured at 110 K. Sudden step-like jumps are again visible in the 1.6-μm wire. Arrows indicate the sweeping directions of the magnetic field for each curve.