Magnetization process of the S=1/2 distorted diamond spin chain with the Dzyaloshinsky-Moriya interaction

The distorted diamond chain has attracted a lot of interest, since the compound Cu3(CO3)2(OH)2, so-called azurite, was revealed to be a good candidate for this system. Although several theoretical studies were performed, the strong anisotropy observed in the magnetization measurement of azurite has not been explained very well. To solve the mechanism of this anisotropy, we introduce the Dzyaloshinsky-Moriya (DM) interaction suitable for the crystal symmetry of azurite. The numerical diagonalization study on this realistic model indicates that the anisotropy in the experimental magnetization curve would be reproduced with sufficiently large DM interaction. We also propose a mechanism of the field-induced incommensurate order, which was observed above the 1/3 magnetization plateau by the NMR measurement.