La₃CrGe₃Be₂O₁₄ and Nd₃CrGe₃Be₂O₁₄: New magnetic compounds of the langasite family

This communication focuses on recently discovered Ln₃CrGe₃Be₂O₁₄ (Ln = La–Sm) compounds as a new class of low-dimensional magnets. We conducted the first studies of their magnetic properties by means of the magnetic susceptibility, specific heat, and high-resolution optical spectroscopy measurements of the La and Nd representatives. In La₃CrGe₃Be₂O₁₄, which contains only one (chromium) magnetic system, the shortest exchange paths are within isolated chromium chains along the c axis. The compound demonstrates one-dimensional magnetic behavior, i.e., an absence of a long-range order, at least down to 0.4 K, and short-range magnetic correlations with the antiferromagnetic exchange integral along the chains estimated as J_Cr = 4.0 ± 0.5 K. In Nd₃CrGe₃Be₂O₁₄ containing two magnetic subsystems, a splitting of the neodymium Kramers doublets at low temperatures indicates magnetic activity due to both short-range correlations and possible magnetic ordering at 2 K.