Synthesis and study of the chiral magnetic system EuIr2P2

Chiral materials, where no improper symmetry operations such as inversion are present, are systems prone to the appearance of a skyrmion lattice. Recently it has been shown theoretically that not only ferromagnets (FMs) but also antiferromagnets (AFMs) can host such kind of phases. In this work we study a new candidate for AFM skyrmions, ${\mathrm{EuIr}}₂{\mathrm{P}}₂$, by means of magnetization and specific heat measurements on poly and single crystals. X-ray diffraction confirms a trigonal chiral crystal structure, where europium ions form helices along the $c$ direction. In spite of predominantly FM interactions, ${\mathrm{Eu}}²⁺$ ions order antiferromagnetically at ${T}_{{N}₁}=5$ K in what seems to be an incommensurate amplitude-modulated magnetic state where the moments are oriented mainly along the $c$ direction. A second magnetic transition takes place at ${T}_{{N}₂}=2.9$ K, involving the ordering of an in-plane component of the Eu moment likely resulting in an equal-moment structure. Specific heat data show a tail above ${T}_{{N}₁}$. Accordingly the magnetic entropy at ${T}_{{N}₁}$ is strongly reduced in comparison to the expected $Rln8$ value. This evidences a significant amount of frustration. A simple analysis based on a Heisenberg model indicates that the observed properties imply the presence of several relevant interactions, with competing FM and AFM ones resulting in frustration. Thus ${\mathrm{EuIr}}₂{\mathrm{P}}₂$ is a new interesting magnetic system, where chirality and frustration might result in unconventional magnetic textures.