Vortex states of the Ginzburg-Landau functional for the E-u symmetry are theoretically studied in detail. Much attention has been focused on this model in connection with the observed phase diagram of superconducting UPt3. However, its properties over the entire range H-c1 less than or equal to H less than or equal to H-c2 have not been clarified sufficiently. I hen report new results on the model obtained with the Landau-level expansion method; it enables us to (i) calculate the properties of the entire region H-c1 less than or equal to H less than or equal to H-c2 quite accurately as well as emciently, (ii) enumerate possible transitions in the vortex states, and (iii) obtain a reliable phase diagram of multi-order-parameter systems. It is thereby shown that a second-order transition is possible for an arbitrary field direction in this model. Proposals concerning experimental test of its validity for UPt3 are discussed. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 6]
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