EURONS Town Meeting 2008
September 17 - 19, 2008 -
Information

Title:	Dr.
Family Name:	Lima Lopes
First Name:	Armandina
Gender:	female
E-Mail:	armandina.lima.lopescern.ch
Affiliation for Badge:	CFNUL, Lisboa
Institute:	Centro de Física Nuclear da Universidade de Lisboa
Address (Street):	Av. Prof. Gama Pinto, 2
Postal Code, City:	1649-003, Lisboa
Country:	Portugal
Phone:	00 351 217904744
Fax:	00 351 217954288
Young researcher with contribution:	Yes
Arrival Date:	September 16
Departure Date:	September 20
Author(s):	A.M.L. Lopes 1, 2, J.P. Araújo3, V.S. Amaral 4, J.G. Correia 2,5, Y.Tomioka 6 and Y. Tokura 7
Institute(s):	1-Centro de Física Nuclear, Univ. de Lisboa, Portugal 2-CERN, Geneva, Switzerland 3-Departamento de Física, IFIMUP, Univ. do Porto, Portugal 4-Departamento de Física and CICECO, Univ. de Aveiro, Portugal 5-Instituto Tecnólogico Nuclear, Sacavém, Portugal 6-National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan 7-Department of Applied Physics, Tokyo Univ., Japan
Title:	Perturbed Angular Correlation Study in charge ordering Pr$_{1-x}$Ca$_{x}$MnO$_3$ manganites
Abstract:	In the last years mixed valence manganite systems have received considerable attention due to the richness of its phase diagram [1] displaying a variety of phase transitions associated with the spin, lattice, charge and orbital degrees of freedom. Recently, it has been shown that manganites can exhibit coexistence of ferroelectric and ferromagnetic orders and the switching of the electric polarization by a magnetic field was observed in RMnO3 perovskites[2]. To achieve a better understanding on manganite¿s charge ordered state (CO) and, in particular, to ascertain the existence of ferroelectric order in Pr$_{1-x}$Ca$_{x}$MnO$_3$, system nano scale information is crucial. In this work we use the Perturbed Angular Correlation (PAC) spectroscopy study the Electrical-Field Gradients (EFG) of the Pr$_{1-x}$Ca$_{x}$MnO$_3$, system as a function of Ca concentration within the large temperature range. PAC measurements as a function of temperature in samples with Ca concentration, x=0.35, x=0.40 and x=0.85 revealed strong anomalies in the EFG parameters when the system undergoes the CO transition. In particular, the principal component of the EFG presents a sharp discontinuity below the CO transition. This contrasts with samples where no CO occurs, for which the typical EFG behaviour as a function of temperature is observed. Our data in charge order Pr$_{1-x}$Ca$_{x}$MnO$_3$ gives strong evidence for the existence of a paraelectric to ferroelectric discontinuous phase transition decoupled by a few degrees from the charge order transition. References [1] Raveau et al. Phys. Rev

Eurons2008 Registration Main Page