Highly correlated structural, local structural, Raman spectroscopic and magnetic properties of Mn-substituted Cu₂V₂O₇

Low-dimensional quantum spin ½ system Cu₂V₂O₇has been investigated in the framework of Mn-substitution at the Cu site, which is really un-investigated. The studied compounds Cu_{2 -x}Mn_xV₂O₇(x= 0, 0.05, 0.1 and 0.15) have been synthesized and characterized structurally, spectroscopically, local structurally and magnetically via x-ray diffraction, Raman, x-ray absorption and temperature, field dependent magnetization measurements respectively. Although Cu₂V₂O₇can be found inα, βandγ-phase, however all of the studied compounds are found in single orthorhombicα-phase which has crucial magneto-electric application potential. Temperature dependent Raman spectra indicated anharmonic phonon-phonon scattering but there is no spin-phonon coupling for VO₄vibrational modes. The local structure probed via x-ray absorption near edge structure and extended x-ray absorption fine structure spectroscopy at 15 K, 300 K indicates Cu²⁺, V⁵⁺and mixed valent Mn²⁺and Mn³⁺ionic states and justified local structure for the probed ions. Magnetic measurements indicate long-range antiferromagnetic ordering with doping independent Neel temperature (32.5 K). Further observations are strong magnetic hysteresis at 5 K (due to canted spin structure), zero field exchange-bias and their noteworthy enhancement upon Mn-substitution. Interesting correlation between structural parameters and magnetic exchanges has been developed.