Ferrimagnetism of MnV₂O₄spinel

Abstract

The spinel M nV2O4 is a two-sublattice ferrimagnet, with site A occupied by the M n 2+ ion and site B by the V 3+ ion. The magnon of the system, the transversal fluctuation of the total magnetization, is a complicated mixture of the sublattice A and B transversal magnetic fluctuations. As a result, the magnons' fluctuations suppress in a different way the manganese and vanadium magnetic orders and one obtains two phases. At low temperature (0, T * ) the magnetic orders of the M n and V ions contribute to the magnetization of the system, while at the high temperature (T * , TN ), the vanadium magnetic order is suppressed by magnon fluctuations, and only the manganese ions have non-zero spontaneous magnetization. A modified spin-wave theory is developed to describe the two phases and to calculate the magnetization as a function of temperature. The anomalous M (T ) curve reproduces the experimentally obtained ZFC magnetization.PACS numbers: 75.50. Gg, 75.30.Ds, 75.60.Ej, This Letter is inspired from the experimental measurements of the ZFC magnetization of M nV 2 O 4 [1, 2, 3]. The profile of the experimental curve reproduces the anomalous magnetization curve predicted by L. Neel [4,5] for ferrimagnets with equal sublattice spins. This stimulates to model the manganese vanadate spinel in the spirit of the Neel's theory. By comparing and contrasting ZFC and FC magnetization one gains insight into a magnetism of the manganese vanadate oxide.The spinel M nV 2 O 4 is a two-sublattice ferrimagnet, with site A occupied by the M n 2+ ion, which is in the 3d 5 high-spin configuration with quenched orbital angular momentum, which can be regarded as a simple s = 5/2 spin. The B site is occupied by the V 3+ ion, which takes the 3d 2 high-spin configuration in the triply degenerate t 2g orbital, and has orbital degrees of freedom. The measurements show that the set in of the magnetic order is at Neel temperature T N = 56K [1], and that the magnetization has a maximum near T * = 50K. Below this temperature the magnetization sharply decreases and goes to zero when temperature approaches zero.We consider a system which obtains its magnetic properties from M n and V magnetic moments. It is shown that the true magnons in this system, which are the transversal fluctuations corresponding to the total magnetization, are complicated mixtures of the M n and V transversal fluctuations. The magnons interact with manganese and vanadium ions in a different way, and the magnons fluctuations suppress the M n and V ordered moments at different temperatures. As a result, the ferrimagnetic phase is divided into two phases: low temperature phase 0 < T < T * , where the magnetic orders of the M n and V ions contribute to the magnetization of the system, and high temperature phase (T * , T N ), where the vanadium magnetic order is suppressed by magnon fluctuations, and only the manganese ions have non-zero spontaneous magnetization. A modified spin-wave theory is developed to describe the two phases and to calculate the magnetization as a function ...

Model for the field cooled and zero field cooled ferrimagnetic spinel

“…The magnons interact with manganese and vanadium ions in a different way, and the magnons fluctuations suppress the M n and V sublattice magnetizations at different temperatures. As a result, the ferrimagnetic phase is divided into two phases: in the low temperature phase 0 < T < T * the sublattice M n magnetization and sublattice V magnetization contribute to the magnetization of the system, while at the high temperature (T * , T N ), the vanadium sublattice magnetization is suppressed by magnon fluctuations, and only the manganese ions have non-zero spontaneous magnetization 54 . This means that high temperature phase is partial order one and T * is partial order transition temperature.…”

Novel Single‐Crystal‐to‐Single‐Crystal Anion Exchange and Self‐Assembly of Luminescent d10 Metal (CdII, ZnII, and CuI) Complexes Containing C3‐Symmetrical Ligands

“…This kind of metal oxide nanoparticle has garnered a great deal of interest among researchers, owing to the unique properties, for applications in ceramics as catalysts, sensors, semiconductors, magnetic data storage, and solar energy devices. Spinel‐type, related metal oxides and phosphates such as γ‐Fe 2 O 3 , Co 3 O 4 , Mn 3 O 4 , TiO 2 , Ca 0.8 Sr 0.2 Ti (1 − x ) FeO 3 , YSZ, LiFePO 4 , CoFe 2 O 4 , ZnFe 2 O 4 , ZnAl 2 O 4 , CoFe 2 O 4 , and LiMn 2 O 4 19, 8 have been prepared by the above method. Usually, the particles obtained in subcritical‐water conditions are larger than those in supercritical conditions because there is a particle growth with an increase in the residence time.…”

“…Although working on alloys and derived compounds seems to be a necessary objective in the magnetocaloric‐research field, most of them are still expensive or toxic. In this sense, in recent years, much work has focused on studying ceramic materials such as manganese oxides and sulfides, both concerning perovskite‐ and spinel‐structure‐type compounds, such as manganese or cobalt oxides, Pr 0,65 Ca 0.6 Sr 0.4–0.35 MnO 3 and PrSrMnCoO 6 ,6 or the layered perovskite La 1.4 Sr 1.6 Mn 2 O 7 and the MnV 2 O 4 , CdCr 2 S 4 and CuZr 1.86 S 4 spinels 7, 8…”

Tunable Ferrites as Environmentally Friendly Materials for Energy‐Efficient Processes

“…Although working on alloys and derived compounds seems to be a necessary objective in the magnetocaloric-research fi eld, most of them are still expensive or toxic. In this sense, in recent years, much work has focused on studying ceramic materials such as manganese oxides and sulfi des, both concerning perovskite-and spinel-structure-type compounds, such as manganese or cobalt oxides, Pr 0,65 Ca 0.6 Sr 0.4-0.35 MnO 3 and PrSrMnCoO 6 , [ 6 ] or the layered perovskite La [ 7,8 ] For instance, the ferrimagnetic (FiM) MnV 2 O 4 shows a noticeably high value of Δ S (24 J kg − 1 K − 1 for a magnetic fi eld of 4 T) near the Curie temperature, T c (57 K). In this compound, this entropy change is due not only to the spin contribution but also to an orbital contribution around T c .…”