* Corresponding author. Tel.: #81-86-251-8107; fax: #81- 86-251-8087. E-mail address: mnaka@cc.okayama-u.ac.jp (M. Nakanishi). Journal of Magnetism and Magnetic Materials 221 (2000) 301}306 Anomalous "eld-induced magnetic transitions in V  X  (X"S, Se) M. Nakanishi*, K. Yoshimura, K. Kosuge, T. Goto, T. Fujii, J. Takada Faculty of Engineering, Department of Applied Chemistry, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan Received 14 June 2000 Abstract The magnetization of V  S  and V  Se  was measured in pulsed high magnetic "elds up to 39 T. The anomalies were observed in the magnetization curves for both V  S  and V  Se  . For V  S  , the anomaly at lower "eld is thought to correspond to spin #opping. The magnetization curves exhibited saturation for both compounds and the values of the ordered moments for V  S  and V  Se  were estimated to be 1.5 and 1.2   /V from the saturation moments, respectively. Our results support the magnetic structure of V  S  proposed by neutron di!raction measurements.  2000 Elsevier Science B.V. All rights reserved. PACS: 74.62.Bf Keywords: Antiferromagnetism; Magnetic transition; Spin #opping; Vanadium chalcogenide; Magnetization process 1. Introduction Itinerant magnetism has been investigated exten- sively in these decades both experimentally and theoretically. It has been revealed that the e!ect of spin #uctuations plays an important role in the itinerant-electron magnetism [1,2]. Self-consistent renormalization (SCR) theory considers the e!ect of coupling between spin wave modes and accounts for the temperature dependence of magnetic sus- ceptibility, spin-lattice relaxation rate and many other thermodynamic properties in itinerant mag- nets quantitatively. As for the magnetic susceptibil- ity (q), it is revealed that only the components of (q) around the ordering vector Q obeys the Curie}Weiss law. The uniform susceptibility of weakly itinerant antiferromagnets in general does not show an anomaly at Ne H el temperature ¹  , so the existence of the magnetic ordered states must be con"rmed by NMR, neutron di!raction or some other experiments. As a result, the number of the weakly itinerant antiferromagnets discovered is relatively small, compared with that of the weakly itinerant ferromagnets. For some itinerant antifer- romagnets (q) has a component around q"0 as well as q"Q and uniform susceptibility obeys the Curie}Weiss law above ¹  .V  S  is thought to be Magma=21357=Venkatachala=C Mamatha=BG 0304-8853/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 5 0 9 - 6