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  Willers, T.; Cezar, J. C.; Brookes, N.B.; Hu, Z.; Strigari, F.; Körner, P.; Hollmann, N.; Schmitz, D.; Bianchi, A.; Fisk, Z.; Tanaka, A.; Tjeng, L.H.; Severing, A.: Magnetic field induced orbital polarization in cubic YbInNi₄: Determining the quartet ground state using x-ray linear dichroism. Physical Review Letters 107 (2011), p. 236402/1-5

10.1103/PhysRevLett.107.236402

Abstract:
We have been able to induce a linear dichroic signal in the Yb M₅ x-ray absorption white line of cubic YbInNi₄ by the application of a magnetic field. The nonzero integrated intensity of the magnetic field induced dichroic spectrum indicates a net noncubic 4f orbital polarization. A quantitative analysis of the temperature and field strength dependence establishes that the crystal-field ground state is a Γ₈ quartet. The results demonstrate the potential of magnetic field induced linear dichroism as a new powerful approach for the investigation of the degeneracy and orbital degrees of freedom of cubic heavy-fermion and Kondo systems.