Emergence of magnetic order and enhanced magnetoelectric coupling in Lu-doped Sm2BaCuO5

The green-phase compound Sm2BaCuO5 has recently drawn significant attention due to the prominent linear magnetoelectric (ME) coupling effect. Herein, we report a successful chemical doping control of magnetic order and ME effect in Lu3+-doped multiferroic Sm2BaCuO5 . Upon a small amount of Lu3+ doping, it is suggested that the majority of Cu ions interact through Sm3+ and order at TN1 -23 K, whereas some Cu2+ interacting through Lu3+ can lead to another transition at T*-21 K-16 K upon doping Lu3+ ions from 5% to 20%. More interestingly, this emergent magnetic order is concomitant with a broad valley in the pyroelectric current and dielectric anomaly, providing clear evidence of intrinsic coupling between magnetic and ferroelectric orders. In contrast to the parent phase, significant enhancement of the linear ME coefficient is obtained. Our results unveil the importance of interplay of 4f-3d magnetic interactions in inducing ferroelectricity and offer an alternative route to achieve high performance in ME coupling.