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Author Carreras Oropesa, W.G.; Encina, S.; Pedrazzini, P.; Correa, V.F.; Sereni, J.G.; Vildosola, V.; García D.J.; Cornaglia, P.S.
Title Minimal model for the magnetic phase diagram of CeTi1-xScxGe, GdFe1-xCoxSi, and related materials Type Journal Article
Year (down) 2020 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal
Volume 503 Issue Pages 166614
Keywords Magnetism; RTX
Abstract We present a theoretical analysis of the magnetic phase diagram of CeTi1-xScxGe and GdFe1-xCoxSi as a function

of the temperature and the Sc and Co concentration x, respectively. CeScGe and GdCoSi, as many other RTX

(R=rare earth, T=transition metal, X=p-block element) compounds, present a tetragonal crystal structure

where bilayers of R are separated by layers of T and X. While GdFeSi and CeTi0.75Sc0.25Ge are ferromagnetic,

CeScGe and GdCoSi order antiferromagnetically with the R 4f magnetic moments on the same bilayer aligned

ferromagnetically and magnetic moments in nearest neighbouring bilayers aligned antiferromagnetically. The

antiferromagnetic transition temperature TN decreases with decreasing concentration x in both compounds and

for low enough values of x the compounds show a ferromagnetic behavior. Based on these observations we

construct a simplified model Hamiltonian that we solve numerically for the specific heat and the magnetization.

We find a good qualitative agreement between the model and the experimental data. Our results show that the

main magnetic effect of the Sc→Ti and Co→Fe substitution in these compounds is consistent with a change in

the sign of the exchange coupling between magnetic moments in neighbouring bilayers. We expect a similar

phenomenology for other magnetic RTX compounds with the same type of crystal structure.
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Call Number BT @ victor.correa @ Serial 856
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Author Betancourth, D.; Correa, V. F.; Facio, J.I.; Fernández J.; Vildosola, V.; Lora-Serrano, R.; Cadogan, J.M.; Aligia, A.A.; Cornaglia, P.S.; García D.J.
Title Magnetostriction reveals orthorhombic distortion in tetragonal Gd compounds Type Journal Article
Year (down) 2019 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 99 Issue Pages 134406
Keywords
Abstract We report detailed thermal expansion and magnetostriction experiments on GdCoIn5 and GdRh(In1−xCdx )5

(x = 0 and 0.025) single-crystal samples that show a sudden change in the dilation at a field B for temperatures

below the Néel transition temperature TN . We present a first-principles model including crystal-field effects,

dipolar and exchange interactions, and the dependence of the latter with lattice distortions in order to fully

account for the magnetostriction and magnetic susceptibility data. The mean-field solution of the model shows

that a transition between metastable states occurs at the field B. It also indicates that two degenerate phases

should coexist at temperatures below TN , which may explain the lack of observation, in high-resolution

x-ray experiments, of an orthorhombic distortion at the Néel transition, even though the experimentally

determined magnetic structure breaks the tetragonal symmetry and the magnetoelastic coupling from our model

is significant. These conclusions could be extended to other tetragonal Gd-based compounds that present the

same phenomenology.
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Call Number BT @ victor.correa @ Serial 815
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Author Correa, V. F; Villagrán Asiares, A. G.; Betancourth, D.; Encina, S.; Pedrazzini, P.; Cornaglia, P.S.; García D.J.; Sereni, J. G.; Maiorov, B; Caroca-Canales, N; Geibel, Ch.
Title Strong magnetoelastic effect in CeCo1−xFexSi as Néel order is suppressed Type Journal Article
Year (down) 2019 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 100 Issue Pages 184409
Keywords
Abstract A very strong magnetoelastic effect in the CeCo1−xFexSi alloys is reported. The strength of the magnetostrictive

effect can be tuned upon changing x. The moderate low-temperature linear magnetostriction observed at low

Fe concentrations becomes very large (L

L (16T, 2K) = 3 × 10−3) around the critical concentration xc ≈ 0.23 at

which the long-range antiferromagnetic order vanishes. Upon increasing doping through the nonmagnetic region

(x > xc), the magnetostriction strength gradually weakens again. The interplay between magnetic order and the

Kondo screening appears to cause an enhanced valence susceptibility slightly changing the Ce ions valence,

ultimately triggering the large magnetostriction observed around the critical concentration. Previous studies

of the evolution of the lattice parameters with x as well as magnetization and x-ray absorption spectroscopy

measurements support this hypothesis.
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Call Number BT @ victor.correa @ Serial 842
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Author Facio, J.I.; Betancourth, D.; Cejas Bolecek, N.R.; Jorge, G.A.; Pedrazzini, P.; Correa, V.F.; Cornaglia, P.S.; Vildosola, V.; García D.J.
Title Lattice specific heat for the RMIn5 (R=Gd, La,Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction Type Journal Article
Year (down) 2016 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume 407 Issue Pages 406-4011
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Call Number BT @ victor.correa @ Serial 730
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