On September 25, Physical Review B published online a paper titled "Field-induced magnetization plateau and high-field phase diagram of the multiferroic manganite ErMn₂O₅: An analogy to YMn₂O₅" by the research group of Professor Wang Junfeng at the National Pulsed High Magnetic Field Science Center. 

The magnetically induced multiferroic material system RMn₂O₅ (R = rare earth element, Bi) exhibits rich physical effects under magnetic fields, such as topologically protected magnetoelectric switching (GdMn₂O₅), magnetic recording ferroelectric memory (TbMn₂O₅), and magnetic field-induced polarization flip/reversal (TmMn₂O₅). These unique magnetoelectric responses are closely related to the magnetic moment arrangements of the Mn and R ions. Recently, Wang Junfeng's group, by constructing the high magnetic field magnetoelectric phase diagram of YMn₂O₅, identified the impact of the evolution of Mn ion magnetic moment arrangements on the material's magnetoelectric coupling properties [Phys. Rev. B 110, 014430 (2024)]. Notably, ErMn₂O₅, being isostructural with YMn₂O₅, has almost identical Mn ion orientations. Furthermore, while the R ion magnetic moments in this system generally lie within the ab-plane, the Er ions in ErMn₂O₅ align along the *c*-axis. Therefore, building upon the research on YMn₂O₅, ErMn₂O₅ provides an ideal platform for systematically studying the influence of R ion magnetic moment arrangement on the magnetoelectric properties of RMn₂O₅.

High magnetic field magnetization, electric polarization, and high-field magnetoelectric phase diagram of ErMn₂O₅.

In this work, Wang Junfeng's group systematically studied the responses of magnetization and electric polarization along the three crystallographic axes of ErMn₂O₅ single crystals to varying magnetic fields using magnetization and electric polarization measurement capabilities at the pulsed high magnetic field facility. The study found that at T = 1.6 K, first-order and second-order magnetic phase transitions occur near H~c1~ ~12 T and H~c2~ ~30 T along the *a*-axis, corresponding to the reversal and saturation of polarization, respectively. As temperature increases, H~c1~ slowly shifts towards lower fields and disappears above 10 K, while H~c2~ persists up to 40 K. For the *b*-axis, with increasing magnetic field strength, the low-temperature incommensurate weak ferroelectric phase (ICM2/X) is gradually replaced by the high-temperature commensurate ferroelectric phase (CM/FE1). These magnetoelectric responses are very similar to those in YMn₂O₅, indicating the decisive role of Mn ions within the ab-plane. However, responses outside the ab-plane are completely different, originating from the specific magnetic moment arrangement of the Er ions. Additionally, 1/2 and 3/4-type magnetization plateaus were observed along the *c*-axis, reported for the first time in this material system. Based on these experimental observations, combined with considerations of the crystal/magnetic structure of ErMn₂O₅ and Mn-Mn and Mn-Er magnetic interactions, the origins of the electric polarization and magnetization plateaus were discussed, and a corresponding physical model was proposed. This research promotes a deeper understanding of the influence of Mn and R ion magnetic moment arrangements on magnetoelectric coupling characteristics in the RMn₂O₅ system.

Paper link: https://journals.aps.org/prb/abstract/10.1103/16xl-dntg