Magnetic Phase Diagram of (Ni1−xMgx)O Solid Solutions

A magnetic phase diagram of the (Ni 1− x Mg x )O solid solutions is drawn by the results of elastic magnetic neutron scattering and magnetic measurements. The ranges of homogeneous antiferromagnetism (0 ≦ x ≦0.37), tricritical behaviour or frustrated antiferromagnetism (0.37 < x ≦ 0.6), cluster spin glass (0.6 < x ≦ 0.75) and paramagnetic behaviour of the Ni 2+ spin moments in the ground state ( x ≧ 0.8) are determined. It is shown that diamagnetic Mg 2+ ions serve as a source of a random field inducing an extra diamagnetic moment of value 0.35μ B .