New type of frustrated spin chains in KMgxCu5−xV3O13 (x=0–1) Original Research Article

We synthesized the powder samples of KMgxCu5−xV3O13 (x=0.1∼1) and investigated their magnetic susceptibilities and the magnetization curves up to 47 T. The Curie constant and the Weiss temperature of KMgCu4V3O13 change markedly around 20 K. From the Curie constant estimated from the data between 5 and 10 K, the number of spins in the low-temperature region was estimated to be nlow=8.13%, assuming all the copper spins have S=1/2 and g=2. The magnetization curve of KMgCu4V3O13 at 1.7 K is bent around 20 T and shows a linear increase between 20 and 30 T. The magnetization, Mlinear(H→0), estimated by extrapolating the linear part to 0 T is 0.306μB/f.u. Furthermore, all the x dependences of the Néel temperature TN, nlow, θlow, the magnetic field at spin–flop transition Hsf and Mlinear(H→0) change continuously with x. This indicates that there is no quantum critical region between the frustrated spin chains of KCu5V3O13 and KMgCu4V3O13. The ground states of KCu5V3O13 and KMgCu4V3O13 have been deduced.