Ce Mn Ni 4 : A soft ferromagnet with a high degree of transport spin polarization

Abstract

Abstract:In this letter we introduce a new soft ferromagnetic compound, i.e. CeMnNi 4 , which exhibits a large moment (~4.95µ B /Mn) and high degree of spin polarization. The system has a ferromagnetic transition temperature of 148K. Isothermal magnetization measurements at 5K reveal that the material is a soft ferromagnet with a magnetization saturating at about 500Oe and a coercive field of < 5 Oe. We determine the transport spin polarization of this material from Point Contact Andreev Reflection measurements to be 66% thereby making this material potentially important for spintronic applications. 2With the advent of "spintronics", realizing the ability to inject and manipulate spin polarized electrons in metals and semiconductors has gained particular relevance 1 .The basic philosophy behind this emerging area of research is to be able to inject spin polarized electrons and manipulate the spin as well as the charge to realize novel device schemes and to enhance functionality of existing devices. In this context the search for ferromagnets with a high degree of spin polarization, which can be used as source of spin polarized electrons, has gained particular importance. The forerunner in this class of materials 2 is CrO 2 which exhibits a near complete spin polarization (96%) at the Fermi important to note that though the degree of spin polarization is one of the most important criterion for a spin source, several other factors are also crucial to realize efficient spin injection: These include, the Fermi velocity mismatch between the source and the material in which the electrons are injected, the ease to fabricate the material in thin film form, the robustness of the spin polarization against detrimental effects of disorder and the magnetic properties of the material. Since these requirements are expected to be 3 different for different applications, identifying ferromagnets with a large degree of spin polarization is crucial for the progress of spintronics.In this letter we introduce a new ferromagnetic material, namely, CeMnNi 4 , with a T c~1 40K which exhibits a large degree of transport spin polarization 8 . This material is derived from the Pauli paramagnet CeNi 5 9 , by substituting one Ni-site with Mn in the parent compound. Magnetic measurements on CeMnNi 4 show that this material is a soft ferromagnet with a technical saturation at about 4kOe and a coercive field of less than 5Oe. Point Contact Andreev Reflection (PCAR) measurements on this compound reveal that the material has a large degree of transport spin polarization.The alloy CeMnNi 4 was prepared by arc-melting the constituents in several steps.In the first step, stoichiometric amounts of Ce and Ni were melted to form Ce+4Ni alloy.Subsequently, small amounts of Mn (~20mg) is added to the alloy obtained from the previous melt and the alloy is re-melted till until the required amount of Mn is reacted to obtain CeMnNi 4 . In each step the weight of the alloy is monitored and any weight loss due to the volatile Mn is compensated by taking extra ...

Physical properties of single crystalline CeNi4.2Mn0.8

“…It is a soft ferromagnet with coercive field below 5 Oe at 5 K. The saturation field is about 1.5 kOe. Simultaneously, the Andreev reflection measurements have shown [3] that this compound can reach a spin polarization of the order of 66%. Typical values for 3d ferromagnetic metals do not exceed 40% and only half-metallic Heusler compounds or manganites like La 0.7 Sr 0.3 MnO 3 can compete with CeNi 4 Mn.…”

“…the spintronics) is based on the spin polarization effects. Recently it has been found [1][2][3] that CeNi 4 Mn exhibits exceptional and promising properties. It is a soft ferromagnet with coercive field below 5 Oe at 5 K. The saturation field is about 1.5 kOe.…”

Spin-glass behavior in CeCuxNi4−xMn and Ce0.9Nd0.1Ni4Mn compounds

“…CeCu 4 Mn has been previously suggested to show signatures of the spin-glass (SG) behavior based on the pronounced difference between the ZFC (zero-field cooling) and FC (field cooling) magnetic susceptibility and the lack of anomaly in the heat capacity [7]. Therefore, one should observe evolution of the magnetic parameters substituting gradually Ni by Cu.…”

From Heavy Fermion and Spin-Glass Behavior to Magnetic Order in CeT4M Compounds

“…1, CeNi 4 Mn and CeCu 4 Mn represent a ferromagnetic and a spin-glass material, respectively. CeNi 4 Mn is a soft ferromagnet [29], which due to the magnetic moment close to integer value and high degree of spin polarization was suspected to be a half metal this was not conrmed in further studies. Among the systems drawn in Fig.…”