Moein Adnani

Third Prize; Advisor: C. W. Chu
Ph.D. student in Physics; "Magnetoelectric Effect in New Type II Multiferroic HoFeWO6"


Abstract: Multiferroic materials are a type of materials with at least two coexisting ferroic orders. As a result, they are a promising candidate to exhibit a strong linear magnetoelectric effect. This coupling of orders is important from a technological point of view since it has the potential for smaller and more efficient devices.  

In this work, we investigated multiferroicity and magnetoelectric effect in HoFeWO6 with a polar structure of Pna21. This compound shows an antiferromagnetic transition at TN=17.8 K with an onset of ferroelectric transition at the same temperature. We found that the electric polarization starts to decrease by further lowering the temperature after the initial increase up to the temperature T*. We also observed that at lower temperatures it shows a magnetodielectric effect with double hysteresis behavior and an increase of ~3.5 % in dielectric constant where the effect disappears as temperature increases. 

A proposed phase diagram was constructed from the measurements taken to date, however additional measurements are still needed to confirm as well as identify the order of the observed transitions and more importantly identify the underlying mechanism behind the observed ferroelectricity.