The intermetallic NdNiMg15 is the Mg-richest phase (more than 88 atom % of Mg) discovered in the Mg–Nd–Ni system. Its structure was determined by X-ray diffraction on single crystal with the following crystal data: tetragonal system, P4/nmm, Z = 2, a = 10.0602(1) Å, c = 7.7612(2) Å, dcalc = 2.40 g·cm–3. Its structure is made of a three-dimensional framework of magnesium atoms showing channels filled by one-dimensional chain consisting of alternating Nd and Ni atoms along the c-axis. Anti-ferromagnetic ordering was observed with TN = 9 K, which is remarkably high considering the long distances between magnetic atoms, that is, Nd atoms. The effective magnetic moment μeff is equal to 3.58 μB, which is consistent with magnetic Nd3+ ions and weakly or nonmagnetic Ni atoms. Below TN, the M(H) curves show field-induced metamagnetic transitions at critical fields increasing with decreasing temperatures. The magnetic structure of NdNiMg15 was determined from neutron powder diffraction data by considering the propagation vector k = (1/2 1/2 0). This magnetic structure consists in ferromagnetic chains along the c-axis of Nd atoms carrying moments, only separated by Ni atoms. The chains are ferromagnetically coupled within planes perpendicular to the [110] direction, and these planes are anti-ferromagnetically coupled to neighboring planes forming a checkerboard-like magnetic structure.< Leer menos