Structural, magnetic and electric-polarization properties of geometrically frustrated YBaCo₄O₇and DyBaCo₄O₇cobaltites

¹ Department of Physics, Indian Institute of Technology - Kharagpur 721302, India
² Solid State Physics Division, Bhabha Atomic Research Centre - Mumbai 400085, India
³ Homi Bhabha National Institute - Anushaktinagar, Mumbai 400094, India
⁴ UGC-DAE Consortium for Scientific Research - Khandwa Road, Indore, 452017, Madhya Pradesh, India
⁵ Cryogenic Engineering Centre, Indian Institute of Technology - Kharagpur 721302, India

^(a) dsekhar2liitkgp@gmail.com

Received: 21 June 2019
Accepted: 13 September 2019

Abstract

In the RBaCo₄O₇ (R = Ca, Y and rare earth) cobaltite family, only CaBaCo₄O₇ shows 3D long-range ferrimagnetic and spin-driven electric-polarization properties. In the present study, we have investigated the structural, magnetic and electric polarization properties in YBaCo₄O₇ and DyBaCo₄O₇ members of this family and the obtained results are compared with the CaBaCo₄O₇. The compound YBaCo₄O₇ showed a series of magnetic transitions in agreement with the reported literature, additionally, a cluster glass behavior below 5 K is observed. Powder neutron diffraction studies on DyBaCo₄O₇ cobaltite showed an orthorhombic Pbn2₁ symmetry and signature of short-range 120° magnetic correlations of kagome layer and a spin glass behavior below 65 K. Dielectric measurements on both the samples showed strong frequency dispersion at high-temperature and frequency-independent behavior at low temperature without dielectric anomaly. Pyroelectric current measurement has showed a broad peak around 50 K in both the samples; however, a careful analysis relates the peak to thermally stimulated depolarization current. This study signifies that the giant structural distortions and cobalt charge ordering at the kagome layer are the key factors to drive both long-range magnetic ordering and spin-driven electric polarization in this cobaltite family.