Preformed nanoscale ferromagnetism in manganites

¹ Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University Piscataway, NJ 08854, USA
² Department of Materials Science, Osaka Prefecture University - Osaka 599-8531, Japan
³ Advanced Nano Characterization Center, National Institute for Materials Science (NIMS) Tsukuba 305-0044, Japan
⁴ Department of Materials Science and Engineering, Nagoya Institute of Technology - Nagoya 466-8555, Japan
⁵ Center for Condensed Matter Sciences, National Taiwan University - Taipei 106, Taiwan

^(a) mori@mtr.osakafu-u.ac.jp

Received: 6 October 2012
Accepted: 28 November 2012

Abstract

In order to clarify the electronic phase separation consisting of distinct ferromagnetic (FM) metallic and charge-ordered (CO) insulating phases in the colossal magnetoresistive (La, Pr, Ca)MnO₃, we have carefully examined the electronic inhomogeneities by Lorentz microscopy, combined with conventional magnetic studies. We discovered the presence of an intermediate FM state characterized by the emergence of nanoscale (10–20 nm) magnetic regions (magnetic nano-droplets) in the intermediate temperature window above the FM transition temperature. The magnetic nano-droplets in fact precede the onset of ferromagnetic long-range order. It is also found that this intermediate state with magnetic nano-droplets is intimately coupled with the presence of the short-range CO regions.