A compensation temperature induced by transverse fields in a mixed spin-1 and spin- 3 2 Ising ferrimagnetic system * ) O. F. Abubrig, A. Bob´ ak, D. Horv´ ath, M. Jaˇ sˇ cur DepartmentofTheoreticalPhysicsandGeophysics,FacultyofScience, P.J. ˇ Saf´ arikUniversity,Moyzesova16,04154Koˇ sice,Slovakia Received 8 October 2001 A mean-field theory is developed for a mixed Ising ferrimagnetic system consisting of spin 1 and spin 3 2 with different transverse fields. The phase diagram and the thermal behaviour of magnetizations are studied. We find that a compensation point induced by different transverse fields can be observed, although the system never exhibits any compensation point for either zero or uniform transverse fields. The anomalous behaviour of the initial longitudinal magnetic susceptibility in the vicinity of the compensation and critical temperatures is also obtained. PACS : 75.10.-b, 75.30.Kz, 75.50.Gg Key words : ferrimagnet, transverse field, compensation temperature, susceptibility 1 Introduction In the last decade there has been an increasing number of works dealing with magnetic properties of two-sublattice mixed-spin Ising systems consisting of two magnetic atoms A and B with spins s A and s B (see, for example [1] and refer- ences therein). They are studied not only for purely theoretical interest but also because they have been proposed as possible models to describe ferrimagnetism in molecular-based magnetic materials [2]. Most of these studies treat the mixed-spin Ising system with s A =1/2 and s B = s (s> 1/2) in a single-ion anisotropy field, located on separate sublattices. On the other hand, some attention has recently been directed to mixed-spin Ising systems where both constituents have spin values larger than 1/2 [3–6]. In particu- lar, the effects of the different single-ion anisotropies on the transition temperature and the temperature dependencies of magnetizations of the mixed spin-1 and spin- 3 2 Ising ferrimagnetic system have been investigated by the use of the effective-field theory with correlations [4] and the mean-field theory [6]. The existence of one or even two compensation points for this system has also been discussed. As far as we know, however, the effects of transverse fields on the magnetic properties of the mixed spin-1 and spin- 3 2 Ising system have not been studied yet. Therefore, the main purpose of this work is to clarify whether the present system may exhibit a compensation point under different transverse fields and also show some character- istic effects of transverse fields on the transition temperature, magnetization curves and initial longitudinal susceptibility, using the mean-field theory. * )Presented at 11th Czech and Slovak Conference on Magnetism, Koˇ sice, 20–23 August 2001 Czechoslovak Journal of Physics, Vol. 52 (2002), No. 2 131