The spin glass-antiferromagnetism competition in Kondo-lattice systems in the presence of a transverse applied magnetic field

A theory is proposed to describe the competition among antiferromagnetism (AF), spin glass (SG) and Kondo effect. The model describes two Kondo sublattices with an intrasite Kondo interaction strength JK and a random Gaussian interlattice interaction in the presence of a transverse field Γ. The Γ field is introduced as a quantum mechanism to produce spin flipping and the random coupling has average −2J0/N and variance 32J/N . The path integral formalism with Grassmann fields is used to study this fermionic problem, in which the disorder is treated within the framework of the replica trick. The free energy and the order parameters are obtained using the static ansatz. In this many parameters problem, we choose J0/J ≈ (JK/J) 2 and Γ/J ≈ (JK/J) 2 to allow a better comparison with the experimental findings. The obtained phase diagram has not only the same sequence as the experimental one for Ce2Au1−xCoxSi3, but mainly, it also shows a qualitative agreement concerning the behavior of the freezing temperature and the Neel temperature which decreases until a Quantum Critical Point (QCP). The competition between RKKY interaction and Kondo effect has a fundamental role in Ce and U compounds [1]. The presence of disorder in alloys can deeply affect such competition and, therefore, it can lead a quite intriguing issue. For instance, the CeAu1−xCoxSi3 alloy has a phase diagram which displays the sequence of phases spin glass (SG), antiferromagnetism (AF) and a Kondo state when the chemical disorder is increased by substituting Co in the cited alloy [2]. Moreover, the Neel temperature decreases until reaching a Quantum Critical Point (QCP) at some particular value of the Co content, with no evidence of Non-Fermi Liquid behaviour. Earlier theoretical effort [3] has studied the competition among spin glass, antiferromagnetism and Kondo effect based on a framework previously introduced to study the presence of SG in disordered Kondo lattice [4]. The problem [email protected]