Coexistence of long-ranged charge and orbital order and spin-glass state in single-layered manganites with weak quenched disorder

¹  Spin Superstructure Project (ERATO-SSS), JST, AIST Central 4 - Tsukuba 305-8562, Japan
²  ERATO Multiferroics Project, JST, c/o Department of Applied Physics, University of Tokyo - Tokyo 113-8656, Japan
³  Institute of Multidisciplinary Research for Advanced Materials, Tohoku University - Sendai 980-8577, Japan
⁴  Cryogenic Research Center (CRC), University of Tokyo - Bunkyo-ku, Tokyo 113-0032, Japan
⁵  Correlated Electron Research Center (CERC), AIST Central 4 - Tsukuba 305-8562, Japan
⁶  Department of Applied Physics, University of Tokyo - Tokyo 113-8656, Japan

Corresponding author: rmathieu@kth.se

Received: 9 April 2007
Accepted: 3 September 2007

Abstract

The relationship between orbital and spin degrees of freedom in the single crystals of the hole-doped PrCaMnO₄, 0.3 ≤ x ≤ 0.7 has been investigated by means of ac-magnetometry and charge transport. We show that in an intermediate underdoped region, with 0.35 ≤ x < 0.5, the “orbital-master spin-slave” relationship commonly observed in half-doped manganites does not take place. The long-ranged charge-orbital order is not accompanied by an antiferromagnetic transition at low temperatures, but by a frustrated short-ranged magnetic state bringing forth a spin-glass phase. We discuss in detail the nature and origin of this true spin-glass state, which, as in the half-doped manganites with large quenched disorder, is not related to the macroscopic phase separation observed in crystals with minor defects or impurities.