Multiferroic properties of Ruddlesden-Popper Ca3Mn2O7 with La/Fe co-doping

Here, we mainly report the magnetic properties, dielectric and ferroelectric properties and magnetoelectric coupling effects of ion pairs composed of rare earth element La and transition metal element Fe on A/B co-doped Ca3Mn2O7 samples. It is found that the antiferromagnetic transition occurred near the Ne<acute accent>el temperature (TN) of 102 K, and T N does not change with the increase of doping amount. Below T N , the antiferromagnetic state competes with the ferromagnetic state, showing the spin glass-like behavior. The results of XPS show that there are Mn3+, Mn4+, Fe2+, Fe3+ in the samples, and the ferromagnetic state may be caused by the double exchange interactions between different valence ions. In addition, the peak intensity of pyroelectric current below T N is also regulated by the magnetic field, indicating that the LaxCa3-xFexMn2-xO7 (x=0.4, 0.6, 0.8) series samples have magnetoelectric coupling effect. Meanwhile, observing strong dielectric relaxation behavior near room temperature may be caused by polaron hopping process of electron between transition metal ions with different valences. When magnetic field is applied, the dipole arrangement of various valence ions is blocked, which proves that the doped sample has a strong magnetodielectric (MD) effect. The doping amount is x=0.6, and the MD value is close to 40 %. Therefore, A/B co-doping is an effective method to promote the modification of bilayered Ruddlesden-Popper perovskite Ca3Mn2O7.