Abstract
Nitride perovskites are a recently opened class of materials with a limited number of stable compounds. Notably, anion-vacancy-ordered materials such as LaNiO(2)-type nitrides are rare despite useful properties such as superconductivity reported for analogous oxides. Here, we report the preparation of two LnReN(2) (Ln = Pr, Nd) materials with a distorted LaNiO(2)-type structure at high-pressure, high-temperature conditions of a large volume press. Powder X-ray and neutron diffraction show that the orthorhombic distortion (o-LnReN(2)) of the LaNiO(2)-aristotype structure is caused by buckling of the ReN(4/2) layers through Re dimerization. Electronic structure analysis reveals that the o-LnReN(2) materials are composed of classic nitridometallate anions and a cationic intermetallic framework. Moreover, the calculations reveal the driving force of the Re dimerization likely to be from an electronic instability related to a Peierls-type distortion. We further characterize the magnetic ground state of both materials with magnetization measurements as well as magnetic neutron scattering uncovering a long-range antiferromagnetic order of Nd(3+) moments in NdReN(2) at T(N) = 15.5 K. The stability of the compounds is investigated by temperature-dependent powder X-ray diffraction showing decomposition of NdReN(2) at ca. 750 °C. The o-LnReN(2) materials represent a curious class of nitrides at the border of classic nitridometallates, intermetallics, and low-dimensional complex chemistry.