Investigation of the physical properties of the tetragonal CeMAl4Si2 (M = Rh, Ir, Pt) compounds

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The synthesis, crystal structure, and physical properties studied by means of x-ray diffraction, magnetic, thermal and transport measurements of CeMAl₄Si₂ (M = Rh, Ir, Pt) are reported, along with the electronic structure calculations for LaMAl₄Si₂ (M = Rh, Ir, Pt). These materials adopt a tetragonal crystal structure (space group P4/mmm) comprised of BaAl₄ blocks, separated by MAl₂ units, stacked along the c-axis. Both CeRhAl₄Si₂ and CeIrAl₄Si₂ order antiferromagnetically below Tₙ₁=14 and 16 K, respectively, and undergo a second antiferromagnetic transitition at lower temperature (Tₙ₂=9 and 14 K, respectively). CePtAl₄Si₂ orders ferromagnetically below TC =3 K with an ordered moment of μsat=0.8 μB for a magnetic field applied perpendicular to the c-axis. Electronic structure calculations reveal quasi-2D character of the Fermi surface.