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Author  |
Betancourth, D.; Correa, V.F.; García, D.J. |
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Title |
Evidence of a Low Energy Anisotropy in GdCoIn_5 |
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Journal Article |
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2015 |
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Journal of Low Temperature Physics |
Abbreviated Journal |
J. Low Temp. Phys. |
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179 |
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1-2 |
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90-93 |
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Rare earth magnetism; Antiferromagnetic transition; Anisotropy |
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We investigate the effects of an applied magnetic field on the magnetic properties of the antiferromagnet GdCoIn 5 . The prominent anisotropy observed in the susceptibility below TN is rapidly suppressed by a field of just a few Tesla. Further evidence of this low energy-scale is obtained from magnetoresistance and magnetostriction experiments. The lattice length, particularly, shows a sudden change below 2 T when the magnetic field is applied perpendicular to the crystallographic c^ -axis. |
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Springer US |
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0022-2291 |
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BT @ pedrazp @ |
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710 |
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Carreras Oropesa, W.G.; Correa, V.F.; Sereni, J.G.; García, D.J.; Cornaglia, P.S. |
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Title |
Landau theory for magnetic and structural transitions in CeCo0.85Fe0.15Si |
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Journal Article |
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2018 |
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Journal of Physics: Condensed Matter |
Abbreviated Journal |
J. Phys.: Condens. Matter |
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30 |
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295803 |
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We present a phenomenological analysis of the magnetoelastic properties of CeCo0.85Fe0.15Si
at temperatures close to the Néel transition temperature TN. Using a Landau functional we
provide a qualitative description of the thermal expansion, magnetostriction, magnetization
and specific heat data. We show that the available experimental results (Correa et al 2016 J.
Phys.: Condens. Matter 28 346003) are consistent with the presence of a structural transition
at Ts TN and a strong magnetoelastic coupling. The magnetoelastic coupling presents a
Janus-faced effect: while the structural transition is shifted to higher temperatures as the
magnetic field is increased, the resulting striction at low temperatures decreases. The strong
magnetoelastic coupling and the proximity of the structural transition to the onset temperature
for magnetic fluctuations, suggest that the transition could be an analogue of the tetragonal to
orthorhombic observed in Fe-based pcnictides. |
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BT @ victor.correa @ |
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796 |
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Carreras Oropesa, W.G.; Encina, S.; Pedrazzini, P.; Correa, V.F.; Sereni, J.G.; Vildosola, V.; García D.J.; Cornaglia, P.S. |
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Title |
Minimal model for the magnetic phase diagram of CeTi1-xScxGe, GdFe1-xCoxSi, and related materials |
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Journal Article |
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Year |
2020 |
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Journal of Magnetism and Magnetic Materials |
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503 |
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166614 |
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Magnetism; RTX |
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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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BT @ victor.correa @ |
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856 |
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Author |
Correa, V.F.; Betancourth, D.; Sereni, J.G.; Caroca-Canales, N.; Geibel, C. |
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Title |
Remarkable magnetostructural coupling around the magnetic transition in CeCo0.85Fe0.15Si |
Type |
Journal Article |
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Year |
2016 |
Publication |
Journal of Physics: Condensed Matter |
Abbreviated Journal |
J. Phys.: Condens. Matter |
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28 |
Issue |
34 |
Pages |
346003 |
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Keywords |
magnetostriction, cerium compounds, magnetism |
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We report a detailed study of the magnetic properties of CeCo0.85Fe0.15Si under high magnetic
fields (up to 16 Tesla) measuring different physical properties such as specific heat, magnetization,
electrical resistivity, thermal expansion and magnetostriction. CeCo0.85Fe0.15Si becomes
antiferromagnetic at TN 6.7 K. However, a broad tail (onset at TX 13 K) in the specific heat
precedes that second order transition. This tail is also observed in the temperature derivative of
the resistivity. However, it is particularly noticeable in the thermal expansion coefficient where it
takes the form of a large bump centered at TX. A high magnetic field practically washes out that tail
in the resistivity. But surprisingly, the bump in the thermal expansion coefficient becomes a well
pronounced peak fully split from the magnetic transition at TN. Concurrently, the magnetoresistance
also switches from negative to positive above TN. The magnetostriction is considerable and
irreversible at low temperature ( (16 T) 4×10− L
L
4 at 2 K) when the magnetic interactions
dominate. A broad jump in the field dependence of the magnetostriction observed at low T may be
the signature of a weak ongoing metamagnetic transition. Taking altogether the results indicate the
importance of the lattice effects on the development of the magnetic order in these alloys. |
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BT @ victor.correa @ |
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732 |
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Author |
Correa, V.F.; Curci, I.; Sereni, J.G.; Caroca Canales, N.; Geibel, C. |
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Title |
Magnetic-field-tuned valence susceptibility in CeCo1−xFexSi revealed by magnetostriction |
Type |
Conference Article |
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Year |
2022 |
Publication |
Journal of Physics: Conference Series |
Abbreviated Journal |
J. Phys.: Conf. Ser. |
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Volume |
2164 |
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012042 |
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We report magnetoelastic studies in the CeCo1−xFexSi alloys. Iron doping has a profound effect on the low temperature linear magnetostriction. At T = 2 K, the strength of the magnetostriction peaks at x = 0.23 where it reaches a value as large as $\[\frac{{\Delta L}}{L} = 3 \times {10^{ – 3}}\]$ in an applied magnetic field B = 16 T. This Fe concentration corresponds to the critical one xc above which long-range antiferromagnetic order is no longer observed. The progressive increment of the hibridization between the Ce 4f orbital and the conduction band, as the magnetic order vanishes, gives rise to a sizeable valence susceptibility that can be finely tuned by the magnetic field explaining the large magnetostrictive effect around xc. At higher x, the magnetostriction decreases, in agreement with a weaker valence susceptibility resulting from a stronger hibridization. |
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BT @ victor.correa @ |
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880 |
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Correa, V.F.; Francoual, S.; Jaime, M.; Harrison, N.; Murphy, T.P.; Palm, E.C.; Tozer, S.W.; Lacerda, A.H.; Sharma, P.A.; Mydosh, J.A. |
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Title |
High magnetic field lattice length changes in URu2Si2 |
Type |
Journal Article |
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Year |
2012 |
Publication |
Physical Review Letters |
Abbreviated Journal |
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Volume |
109 |
Issue |
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Pages |
246405 |
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We report high-magnetic-field (up to 45 T) ^ c-axis thermal-expansion and magnetostriction experiments on URu2Si2 single crystals. The sample length change associated with the transition to the ‘‘hidden order’’ phase becomes increasingly discontinuous as the magnetic field is raised above 25 T. The
reentrant ordered phase III is clearly observed in both the thermal expansion and magnetostriction above 36 T, in good agreement with previous results. The sample length is also discontinuous at the boundaries of this phase, mainly at the upper boundary. A change in the sign of the coefficient of thermal expansion is observed at the metamagnetic transition (BM 38 T), which is likely related to the existence of a quantum critical end point. |
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BT @ victor.correa @ |
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651 |
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Author |
Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G. |
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Title |
Order-disorder transition and the zero-dimensional vortex pinning regime in Bi2Sr2CaCu2O8+delta |
Type |
Journal Article |
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2001 |
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PHYSICAL REVIEW B |
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63 |
Issue |
9 |
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092502 |
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We make a comparative study between the ab plane's dc critical current and the ac transverse magnetic permeability μ(perpendicular to) in the Campbell limit for optimally doped and overdoped Bi2Sr2CaCu2O8+delta samples. We focus attention on the low-temperature region [T/T-c(0) < 0.25], where the transition to the zero-dimensional Larkin limit is detected by the critical current as well as by a rapid change of the Labusch parameter with temperature. The order-disorder transition, characterized by the second peak in magnetization, disappears in the presence of this zero-dimensional pinning regime. |
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0163-1829 |
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ISI:000167312000016 |
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BT @ hernan @ |
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218 |
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Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G. |
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Onset of the 0-dimensional vortex pinning behavior in the optimally doped and overdoped Bi2Sr2CaCu2O8+delta system |
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Journal Article |
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2000 |
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PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS |
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341 |
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1285-1286 |
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We report results of transverse AC magnetic permeability in the linear regime and DC magnetization loops for optimally doped and oxygen overdoped samples of Bi2Sr2CaCu2O8+delta The data cover the low temperature (T < 25K) and low held (H-a < 1000 Oe) region of the magnetic (H-a-T) phase diagram. In optimally doped as well as in overdoped samples a crossover to a O-dimensional pinning regime (Larkin length, L-C(C), shorter than the inter-plane CuO2 distance) is observed at a characteristic temperature Too for all investigated fields. The order-disorder transition, identified by the second peak in magnetization and a non monotonous field dependence of the AC penetration depth, is quenched below T-0D. |
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0921-4534 |
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ISI:000165855700242 |
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BT @ hernan @ |
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221 |
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Correa, V.F.; Kaul, E.E.; Nieva, G. |
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Overdoping effects in Bi2Sr2CaCu2O8+delta: From electromagnetic to Josephson interlayer coupling |
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2001 |
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PHYSICAL REVIEW B |
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63 |
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17 |
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172505 |
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We report a study of magnetic, structural, and transport properties of Bi2Sr2CaCu2O8+delta single crystals with different degrees of overdoping. The overdoping is achieved by high oxygen pressure (up to 190 bar) annealing. The parameters used to characterize the overdoping were the crystallographic c-axis lattice parameter and the superconducting transition temperature. The irreversibility line H-il and the characteristic field of the order-disorder transition of the vortex structure H-sp were obtained from dc magnetization with the applied magnetic field perpendicular to the CuO2 planes. The large overdoped range has two well-defined regions: (i) close to the optimal doping the interlayer coupling is mainly electromagnetic and H-sp is given by Phi (0)/lambda (2)(ab) (0) [lambda (ab)(0) is the in-plane penetration depth at T = 0 K], and (ii) with further overdoping the Josephson interlayer coupling becomes relevant, so H-sp deviates from Phi (0)/lambda (2)(ab) (0) and is fixed by the effective-mass anisotropy. All the results indicate an increase in the coupling between CuO2 planes with overdoping. |
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ISI:000168487300034 |
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BT @ hernan @ |
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216 |
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Correa, V.F.; Nieva, G.; de la Cruz, F. |
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Vortex softening: Origin of the second peak effect in Bi2Sr2CaCu2O8+delta |
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2001 |
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PHYSICAL REVIEW LETTERS |
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87 |
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5 |
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057003 |
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Magnetic hysteresis and transverse ac permeability measurements in Bi2Sr2CaCu2O8+delta allow a comparative analysis of the critical current with the elastic response of vortex structures, in equilibrium with their pinning potential, in the field and temperature region where the second peak is detected. This study provides strong evidence that the second peak has its origin in changes of the elastic equilibrium properties of the vortex structures. |
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0031-9007 |
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ISI:000170212200049 |
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