Effect of Ru doping on magnetoresistance and magnetocaloric effect in Bi0.4Ca0.6Mn1-xRuxO3 (0<=x<=0.2)
Abstract
We show that Ru doping in Bi0.4Ca0.6Mn1-xRuxO3, unlike other magnetic ions, destabilizes charge ordering and transforms the charge-ordered antiferromagnetic insulator (x=0) into a ferromagnetic metal for x≥0.1. The ferromagnetic transition temperature (TC) increases from TC=130 K for x=0.1 to 272 K for x=0.2 and the resistivity of the later compound at 10 K is eight orders of magnitude lower than that of x=0. The magnetoresistance at H=7 T has a maximum value (-98%) for x=0.05 but it decreases to -20% for x=0.2. While magnetic entropy (ΔSm) for x=0.05 is positive just above the charge ordering temperature, it changes sign with lowering temperature, and is negative over a wide temperature range for x=0.1 and 0.2. The x=0.2 sample shows the highest value of ΔSm=-1.83 J/kg K for ΔH=5 T in the series. Our results suggest that while Ru doping induces ferromagnetic clusters locally in the charge-ordered matrix for x=0.05, charge ordering is completely absent in x=0.2. The greater ability of Ru to induce long range ferromagnetism and insulator-metal transition in robust charge-ordered materials such as Bi0.4Ca0.6MnO3 is quite interesting from the point of view of fundamental physics and applications.
- Publication:
-
Journal of Applied Physics
- Pub Date:
- June 2010
- DOI:
- 10.1063/1.3415538
- Bibcode:
- 2010JAP...107k3914K
- Keywords:
-
- antiferromagnetic materials;
- bismuth compounds;
- calcium compounds;
- colossal magnetoresistance;
- ferromagnetic materials;
- ferromagnetic-antiferromagnetic transitions;
- magnetocaloric effects;
- metal-insulator transition;
- 75.47.Gk;
- 75.50.Ee;
- 75.30.Kz;
- 71.30.+h;
- 75.47.Lx;
- Colossal magnetoresistance;
- Antiferromagnetics;
- Magnetic phase boundaries;
- Metal-insulator transitions and other electronic transitions;
- Manganites