The magnetic ordering induced magnetodielectric effect in Ho₂Cu₂O₅ and Yb₂Cu₂O₅

Abstract Materials with strongly coupled magnetic and electronic degrees of freedom provide new possibilities for practical applications. In this paper, we have investigated the structure, magnetic property, and magnetodielectric (MD) effect in Ho2Cu2O5 and Yb2Cu2O5 polycrystalline samples, which possess a non-centrosymmetric polar structure with space group Pna21. In Ho2Cu2O5, Ho3+ and Cu2+ sublattices order simultaneously, exhibiting a typical paramagnetic to antiferromagnetic transition at 13.1 K. While for Yb2Cu2O5, two magnetic transitions which originate from the orderings of Yb3+ (7.8 K) and Cu2+ (13.5 K) sublattices are observed. A magnetic field induced metamagnetic transition is obtained in these two cuprates below Néel temperature (T N). By means of dielectric measurement, distinct MD effect is demonstrated by the dielectric anomaly at T N. Meanwhile, the MD effect is found to be directly related to the metamagnetic transition. Due to the specific spin configuration and different spin evolution in the magnetic field, a positive MD effect is formed in Ho2Cu2O5, and a negative one is observed in Yb2Cu2O5. The spontaneous dielectric anomaly at T N is regarded as arising from the shifts in optical phonon frequencies, and the magnetoelectric coupling is used to interpret the magnetic field induced MD effect. Moreover, an H-T phase diagram is constructed for Ho2Cu2O5 and Yb2Cu2O5 based on the results of isothermal magnetic and dielectric hysteresis loops.