B. Qian et al ., Phys. Rev. B 85, 144427 (2012)

1. Ferromagnetism in CuFeSb: Evidence of competing magnetic interactions in Fe-based superconductorsZhiqiang Mao, Tulane University, DMR 0645305 The study of the interplay between magnetism and superconductivity has been one of the major focuses in current studies on iron pnictides and chalcogenide superconductrs. Iron chalcogenides are characterized by the competition of two magnetic correlations at (,0) and (,) [1,2]; this is distinct from the iron pnictides which display only (,) magnetism [3,4]. A unified mechanism for various AFM states in these Fe -based materials is critical to the understanding of the interplay between superconductivity and magnetism. Mao’s group has recently synthesized a new layered iron-pnictide CuFeSb which shares similar layered tetragonal structure with iron-based superconductors. CuFeSb differs remarkably from Fe-based superconductors in the height of anion Zanion from the Fe plane; ZSb for CuFeSb is ~1.84 Å, much larger than ZAs (1.31-1.51 Å) [3-5] in FeAs compounds and ZTe (~1.77 Å) in Fe1+yTe [2]. In contrast with the metallic antiferromagnetic (AFM) or superconducting state of iron pnictides and chalcogenides under current studies, CuFeSb exhibits a metallic, ferromagnetic state with Tc = 375 K. This finding suggests that the competition between AFM and FM coupling may exist in Fe-based superconductors and that the nature of magnetic coupling within the Fe plane is indeed dependent on the height of anion as predicted in theories [6,7]. • Crystal structure of CuFeSb (P4/nmm), isostructural to Fe-based superconductors. • Lattice parameters at T = 400K: • a = b = 3.93466(2) Å, c = 6.25152(4) Å • bonding angles: • = 93.860(5)°, • =117.797(3)° • No structure transition down to 10K. A remarkable ferromagnetic transition at 375 K, with typical irreversible behavior between zero-field-cooling (ZFC) and field-cooling (FC) histories. B. Qian et al., Phys. Rev. B 85, 144427 (2012)

2. Broader ImpactsZhiqiang Mao, Tulane University, DMR 0645305 1. Involving undergraduate students in the research Provided summer research opportunities for the undergraduates supported by the LA-SiGMA (Louisiana Alliance for Simulation-Guided Materials Applications) REU program. Two students from this program worked with Prof. Mao last summer and they were involved in the research searching for novel superconductor in iron chalcogenides using chemical intercalation. 2. Outreach activity Offered research opportunities to students from Benjamin Franklin High School (BFHS) in New Orleans. Prof. Mao has directed two students from BFHS to complete their independent research project. This project aimed at searching for alternative cathode materials for developing high energy density lithium-ion battery. This project was successful; some promising materials have been found.