High-resolution powder neutron diffraction study of helimagnetic order in CrP1-xVxO4 solid solutions

High-resolution powder neutron diffraction measurements on CrP1-xVxO4 sampl es with x = 0, 0.02, 0.04, 0.06 and 0.08 have yielded precise parameters fo r their low temperature helimagnetic structures which have a magnetic propa gation vector (k(x),0,0). The refined values of k(x) increase from k(x) = 0 .331 for x = 0 to k(x) = 0.337 for x = 0.08 and no tendency of the incommen surate spiral to "lock-in" to the commensurate periodicity k(x) = 1/3 is ob served. The ordered Cr3+ magnetic moment decreases from 2.32(3)mu(B) to 1.7 2(6)mu(B) for x = 0 to x = 0.08. Field and zero-field cooled magnetic susce ptibility measurements evidence increasing static magnetic disorder with x, in agreement with the neutron-diffraction results.