Structure and properties of the integer-spin frustrated antiferromagnetGeNi2O4

Crystal growth of Germanium-based oxide spinels by the Float Zone Method

“…There is a double Ne´el transition temperature, which is consistent with previous measurements [9]. Below these temperatures, field-induced magnetic anisotropy has been found as shown in Fig.…”

“…More recently, a polycrystalline sample of the frustrated antiferromagnet GeNi 2 O 4 (Ni 2þ : 3d 8 ) with integer-spin (S ¼ 1) was reported to exhibit a spin gap based upon specific heat and neutron powder diffraction experiments [9]. GeNi 2 O 4 reveals two magnetic transitions (T N1 ¼ 12:1 K, T N2 ¼ 11:4 K) indicating that the two ordered phases are nearly degenerate.…”

Heat capacities, third-law entropies and thermodynamic functions of the geometrically frustrated antiferromagnetic spinels GeCo2O4 and GeNi2O4 from T=(0 to 400) K

“…This conclusion has been disputed by Plumier [40] who argues that if two sub-lattices exist in GeCo 2 O 4 one should observe two N eel points. Neither the measurements of Plumier nor magnetic susceptibility measurements we report elsewhere [18] show evidence for two N eel points.…”

“…In work we will publish elsewhere, we establish that GeCo 2 O 4 undergoes a subtle cubic to tetragonal phase transition near the magnetic ordering temperature and the unusual shape of the transition may reflect the structural transition superimposed on the transition to long-range order [18].…”

“…A description of the application of the heat capacity data to extract various magnetic parameters such as the magnetic coupling constant and the critical exponents of the magnetic heat capacity anomaly along with results from X-ray, neutron, and magnetic susceptibility studies will be presented in a separate contribution to be published elsewhere [17,18].…”