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Author (up) Facio, J.I.; Betancourth, D.; Pedrazzini, P.; Correa, V. F; Vildosola, V.; García, D. J.; Cornaglia, P.S. url  doi
  Title Why the Co-based 115 compounds are different: The case study of GdMIn5 (M = Co,Rh,Ir) Type Journal Article
  Year 2015 Publication Physical Review B Abbreviated Journal Phys. Rev. B  
  Volume 91 Issue Pages 014409  
  Abstract The discovery in 2001 of superconductivity in some heavy fermion compounds of the RMIn5 (R = 4f or

5f elements; M = Co, Rh, Ir) family, has triggered an enormous amount of research into understanding the

physical origin of superconductivity and its relation with magnetism. Although many properties have been

clarified, there are still crucial questions that remain unanswered. One of these questions is the particular role

of the transition metal in determining the value of critical superconducting temperature (TC). In this work, we

analyze an interesting regularity that is experimentally observed in this family of compounds, where the lowest

N´eel temperatures are obtained in the Co-based materials. We focus our analysis on the GdMIn5 compounds

and perform density-functional-theory-based total-energy calculations to obtain the parameters for the exchange

coupling interactions between the magnetic moments located at the Gd3+ ions. Our calculations indicate that

the ground state of the three compounds is a C-type antiferromagnet determined by the competition between

the first- and second-neighbor exchange couplings inside GdIn3 planes and stabilized by the couplings across

MIn2 planes. We then solve a model with these magnetic interactions using a mean-field approximation and

quantum Monte Carlo simulations. The results obtained for the calculated N´eel and Curie-Weiss temperatures,

the specific heat, and the magnetic susceptibility are in very good agreement with the existent experimental data.

Remarkably, we show that the first-neighbor interplane exchange coupling in the Co-based material is much

smaller than in the Rh and Ir analogs which leads to a more two-dimensional magnetic behavior in the former.

This result explains the observed lower N´eel temperature in Co-115 systems and may shed light on the fact that

the Co-based 115 superconductors present the highest TC.
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  Call Number BT @ victor.correa @ Serial 705  
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