Study of the physical properties of La_2 − xEr_xTi₂O₇ (0 ≤ x ≤ 0.075) compounds

¹ Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 Sfax, Tunisia
² Physics Department, Rabigh College of Science and Art, King Abdulaziz University, P.O. Box 344, 21911 Rabigh, Saudi Arabia
³ I3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal
⁴ Institut Néel, CNRS – Université J. Fourier, BP 166, 38042 Grenoble, France

^a e-mail: essebti@yahoo.com

Received: 14 April 2012
Revised: 16 May 2012
Accepted: 31 May 2012
Published online: 3 August 2012

Abstract

New complex magnetic frustrated materials La_2 − xEr_xTi₂O₇ (0 ≤ x ≤ 0.075) have been synthesized by solid-solid method. The crystallographic and magnetic properties were studied as a function of substitution of the La³⁺ ion by the Er³⁺ one. All samples are found to be single phase and crystallize in the monoclinic structure with P₂₁ space group. Magnetic measurements have revealed the presence of dominant antiferromagnetic interactions and the absence of magnetic ordering until a temperature of 2 K. The magnetic study suggests that the Curie-Weiss temperature (θ_CW) is negative, as expected in the frustrated lanthanide sublattice in the Ln_2 – xLn’_xM₂O₇ structure. From the frustration index f = - θ_CW/T_N, we have deduced the presence of a strong frustration phenomenon. The critical properties of the antiferromagnetic behavior, for x = 0.025, 0.05 and 0.075 samples, have been investigated. It was found that the 2D-self-avoiding walk (SAW) model is the best one to describe the critical phenomena.