Structural, dielectric, antiferromagnetic, and thermal properties of the frustrated hexagonal Ho1-xErxMnO3 manganites

The Er doping effects on the structural, dielectric, ferroelectric, magnetic, and thermal properties of the hexagonal Ho1-xErxMnO3 (0 ≤ x ≤ 1) compounds synthesized by the solid-state reaction method have been investigated by Rietveld refinement and by measurements of dielectric constant, ferroelectric hysteresis loops, magnetic susceptibility, and specific heat. The a lattice parameter decreases as the Er content increases, whereas the c lattice parameter nearly keeps constant with pretty minor fluctuations. Dielectric data and ferroelectric hysteresis loops show all the samples are not only ferroelectric materials with leaky nature, but also with dielectric relaxation related to oxygen vacancies. The magnetizations of these compounds gradually decrease with increasing Er content. The Mn3+ ions in each sample remain stable in the high-spin state in the Mn-O5 trigonal bipyramidal crystal field. Specific heat measurements show that the antiferromagnetic transition temperature continuously rises from 72 K for HoMnO3 to 76 K for ErMnO3. The Debye temperatures are 381 K for ErMnO3 and 422 K for HoMnO3.