标题： 交替磁性多铁材料和交替磁电效应 显示英文标题

标题： Altermagnetic multiferroics and altermagnetoelectric effect

摘要： 磁电多铁材料在低功耗电子器件和推进基础研究方面（包括轴子绝缘体和暗物质探测）受到高度关注。 然而，在传统铁磁体和反铁磁体中，实现铁性自旋和电序的组合以及它们的可控切换仍然是一个重大挑战。 这里，我们首次提出第一性原理的证据，表明在铁电体BaCuF$_4$（T$_N$ $\sim$ 275K）和Ca$_3$Mn$_2$O$_7$（T$_N$ $\sim$ 110K）中可以出现具有相对较高临界温度的时间反演对称性破缺的反铁磁自旋极化。 此外，我们对所有可能的反磁极自旋群进行了分类，揭示了BiFeO$_3$的共线相中的反磁性。 我们还提出了一种反磁电效应，这是一种非相对论性的交叉耦合，涉及晶格结构中非磁性多面体的旋转，将反磁性自旋极化与铁电极化联系起来。 我们的研究结果表明，这为实现高温磁电多铁性和反磁性序参数的电场控制提供了一条替代途径。 显示英文摘要

摘要： Magnetoelectric multiferroics are highly sought after for applications in low-power electronics and for advancing fundamental research, including axion insulators and dark matter detection. However, achieving a combination of ferroic spin and electric orders, along with their controllable switching, remains a significant challenge in conventional ferromagnets and antiferromagnets. Here, we present first-principles evidence that time-reversal symmetry-breaking altermagnetic spin polarization with relatively high critical temperatures can emerge in ferroelectrics BaCuF$_4$ (T$_N$ $\sim$ 275K) and Ca$_3$Mn$_2$O$_7$ (T$_N$ $\sim$ 110K). Furthermore, we classify all possible altermagnetic polar spin groups, revealing altermagnetism in a collinear phase of BiFeO$_3$. We also propose an altermagnetoelectric effect, a nonrelativistic cross-coupling between altermagnetic spin polarization and ferroelectric polarization, mediated by a rotation of nonmagnetic polyhedra in the lattice structure. Our findings suggest an alternative pathway towards high-temperature magnetoelectric multiferroicity and the electric field control of altermagnetic order parameters.