Magnetic Properties of the Q1D Solid Solution Ca_x-1Na_xCr₂O₄ Studied with Neutrons and Muons

In this work we present the results of the measurements carried out by neutron powder diffraction and muon spin rotation/relaxation (μ⁺SR) in ambient and high pressure on the x = 1 (NaCr₂O₄) and x = 0 (CaCr₂O₄) members of the solid soution Ca_1−xNa_xCr₂O₄ and on the intermediate compound x = 0.5 (Ca_0.5Na_0.5Cr₂O₄). The x = 1 results show a unique spin structure where the Cr moments in each zig-zag chain are aligned ferromagnetically along the c-axis, whereas antiferromagnetically along the a-axis between the adjacent zig-zag chains. The x = 0 results show the formation of a complex magnetic order below T_N, that is consistent with an incommensurate AF (IC-AF) order. The investigation on the intermediate compound Ca_1−xNa_xCr₂O₄ showes a fast-relaxing component, possibly indicating a spin-glass state. Moreover, the magnetic order was shown to be almost completely unsensitive to pressures (up to p » 25 kbar), hereby revealing that the effect from the tuning of the spin density of the chains is clearly dominant.