TEMPLATE DESIGN © 2008 www.PosterPresentations.com Anisotropic Kondo Effect in a 3d transition metal compound Ahmad Us Saleheen 1 , Tapas Samanta 1 , Daniel L. Lepkowski 1 , Alok Shankar 1 , Joseph Prestigiacomo 1 , Igor Dubenko 2 , Abdiel Quetz 2 , Iain W. H. Oswald 3 , Gregory T. McCandless 3 , Julia Y. Chan 3 , Philip W. Adams 1 , David P. Young 1 , Naushad Ali 2 , and Shane Stadler 1 1 Department of Physics & Astronomy, Louisiana State University, Baton Rouge, LA 70803 2 Department of Physics, Southern Illinois University, Carbondale, IL 62901 3 Department of Chemistry, The University of Texas at Dallas, Richardson, TX 75080 Abstract Background Results Results Results Conclusion OPTIONAL LOGO HERE We report an anisotropic Kondo effect in purely 3d transition metal ferromagnetic (FM) system (i.e., not rare- earth-based). The isostructural alloying of two compounds having collinear magnetic structure has resulted in a FM Kondo lattice system, Mn 1-x Fe x CoGe in the proximity of a noncollinear FM state with x = 0.2. Resistivity, magnetic susceptibility and heat capacity studies on single crystal sample indicate that the Kondo effect is anisotropic. An increase in resistivity along two principal direction at low- temperature has been observed with the decrease in T, which follows a lnT behavior below the Kondo minimum (T K ) due to Kondo scattering. However, T K along i∥c is about two times higher than that of along i⊥c. Directional dependence of magnetization also mimics the similar behavior by showing pronounced Kondo screening along c-axis. Large saturation magnetization at low-temperature indicates that it is a underscreened Kondo Effect. Underscreening of moments may lead to the coexistence of FM and Kondo behavior. For x=0.2 composition Kadowaki-Woods ratio of 2 ~43 μΏ.cm.mol 2 .K 2 .J -2 was observed. This indicates strong electron correlation in Mn 1-x Fe x CoGe system. According to Rhodes- Wohlfarth model large P C /M S value indicates itinerant behavior (Rhodes and Wohlfarth, Proc.Roy.Soc.London 273,247, 1963). We can see a transition to more itinerant behavior with the increase in Fe content. At x=0.2 composition, a transition from localized to itinerant behavior is expected (Samanta et al.,Appl.Phys.Lett.103,042408, 2013). Resistivity: We observed an increase in ρ at low temperature with the decrease in T. It follows a lnT behavior below the Kondo minimum due to Kondo scattering (inset). T K along i∥c is around two times greater than that of along i⊥c. This behavior may indicate a more pronounced Kondo behavior along c axis. Magnetization: Structure: Single crystals of Mn 0.8 Fe 0.2 CoGe were grown using Sn flux. XRD data indicates a Ni 2 In type hexagonal structure. Lattice parameters are: a=4.06 A 0 and c= 5.20A 0 . Strong anisotropy in both directions is evident from magnetization measurements. Heat Capacity: After fitting the low temperature data a large value of γ= 25.3 mJ/mol K 2 was found, indicating the formation of heavy quantum particle with effective mass enhancement of approximately 30 times that of free electrons. 0 = 15.1 states/eV/f.u. was estimated from the γ value and which is three times larger than that of the parent compound MnCoGe (Samanta et al., 2013). We observed two different Kondo minima in two different axial directions. Until now, the reason for this behavior is not entirely clear to us. We can also see high M S in both directions in spite of Kondo type increase in ρ below T K . From low temperature magnetization data it was revealed that it is an S=1 system. Underscreening of moments may lead to the coexistence of FM and Kondo behavior. Acknowledgement This work is supported by U.S. Dept. of Energy (Grant Nos. DE-FG02-06ER46291,DE-FG02-13ER46946 and DE-FG02- 07ER46420). Ahmad Us Saleheen acknowledges support from LA-SiGMA .