Abstract
We have investigated the rare earth elements dependence on the magnetism to understand the contribution to physical properties of the 4f electrons of (LnO)MnAs (Pn = La, Ce, Pr, Nd). (CeO)MnAs, (PrO)MnAs and (NdO)MnAs shows the antiferromagnetic behaviors at low temperature. (CeO)MnAs and (NdO)MnAs have the magnetic anomalies around 34 K and 24 K, respectively. So, it is speculated that the anomalies depend on the Mn -Mn distance directly
Highlights
Since the iron based superconductors have been found in layered oxypnictide system, two dimensional electronic system consisting of transition metal elements has newly attracted much attention due to the various physical properties such as superconductors in (LaO)FeAs, (LaO)NiAs, (SmO)FeAs[1], ferromagnetic Kondo metal in (LaO)CoAs[2], heavy fermion in (CeO)FeAs[3].In case of Mn oxypnictides, the system (LaO)MnPn (Pn = P, As, Sb) has been reported to antiferromagnetic semiconductors with Neel temperature above room temperature [4]
Considering the insulating origin, there are two scenarios to explain; one is a usual band insulator and the other is a Mott insulator standing on the strong coulomb interaction between the Mn atoms since the Mn 3d5 state in the tetrahedral coordination is thought to be in either low spin state (s = 1/2) providing a metallic character without magnetic moments or a Mott insulating characters, or high spin state (s = 5/2) for a band insulator based on the localization of the Mn 3d magnetic moments
We have investigated the lattice constant dependences of the physical properties by substitution of rare earth elements against La to reveal the insulating origin of the layered Mn oxypnictides
Summary
Since the iron based superconductors have been found in layered oxypnictide system, two dimensional electronic system consisting of transition metal elements has newly attracted much attention due to the various physical properties such as superconductors in (LaO)FeAs, (LaO)NiAs, (SmO)FeAs[1], ferromagnetic Kondo metal in (LaO)CoAs[2], heavy fermion in (CeO)FeAs[3]. In case of Mn oxypnictides, the system (LaO)MnPn (Pn = P, As, Sb) has been reported to antiferromagnetic semiconductors with Neel temperature above room temperature [4]. The Mn 3d magnetic moments in (LaO)MnPn are assumed to order antiferromagnetically at room temperature or above. In case of a Mott insulator, the distance between the Mn atoms which effects on the Coulomb repulsion and the hybridization of the Mn 3d orbitals is very important to decide the physical properties. We have tried changing the Mn -Mn distance by choosing the rare earth element to control the electron correlation between them. If the possible scenario is a Mott insulator and enough controlling the Mn –Mn distance is provided, the system is expected to show the dramatic character change. We have investigated the lanthanoide elements dependences of the physical properties
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