Weakening of charge order and antiferromagnetic to ferromagnetic switch over in Pr_0.5Ca_0.5MnO₃ nanowires

Abstract

We have prepared crystalline nanowires (diameter~50 nm, length ~ a few microns) of the charge-ordering manganite Pr_0.5Ca_0.5MnO₃ using a low reaction temperature hydrothermal method and characterized them using x-ray diffraction, transmission electron microscopy, superconducting quantum interference device (SQUID) magnetometry and electron magnetic resonance measurements. While the bulk sample shows a charge ordering transition at 245 K and an antiferromagnetic transition at 175 K, SQUID magnetometry and electron magnetic resonance experiments reveal that in the nanowires phase, a ferromagnetic transition occurs at~105 K. Further, the antiferromagnetic transition disappears and the charge ordering transition is suppressed. This result is particularly significant since the charge order in Pr_0.5Ca_0.5MnO₃ is known to be very robust, magnetic fields as high as 27 T being needed to melt it.