L. Pedrero

Magnetization study of the energy scales in YbRh2Si2 under chemical pressure

We present a systematic study of the magnetization in YbRh2Si2 under slightly negative (6% Ir substitution) and positive (7% Co substitution) chemical pressure. We show how the critical field H0, associated with the high-field Lifshitz transitions, is shifted to lower (higher) values with Co (Ir) substitution. The critical field HN, which identifies the boundary line of the antiferromagnetic (AFM) phase TN(H) increases with positive pressure and it approaches zero with 6% Ir substitution. On the other side, the crossover field H*, associated with the energy scale T*(H) where a reconstruction of the Fermi surface has been observed, is not much influenced by the chemical substitution. Following the analysis proposed in Refs. 1–4 we have fitted the quantity with a crossover function to indentify H*. The T*(H) line follows an almost linear H-dependence at sufficiently high fields outside the AFM phase, but it deviates from linearity at T ≤ TN(0) and in Yb(Rh0.93Co0.07)2Si2 it changes slope clearly inside the AFM phase. Moreover, the full width at half maximum (FWHM) of the fit function depends linearly on temperature outside the phase, but remains constant inside, suggesting either that such an analysis is valid only for T ≥ TN(0) or that the Fermi surface changes continuously at T = 0 inside the AFM phase.

Magnetic phase diagram of YbCo2Si2 derived from magnetization measurements

We report on high-resolution dc-magnetization (M) measurements on a high-quality single crystal of YbCo2Si2. M was measured down to 0.05K and in fields up to 4T, with the magnetic field oriented along the crystallographic directions [100], [110] and [001] of the tetragonal structure.

Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(In1-xCdx)5

arXiv:1609.01164v1 [cond-mat.supr-con] 5 Sep 2016 Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(In 1−x Cd x ) 5 Dong-Jin Jang 1 † , Luis Pedrero 1 , L. D. Pham 2 , Z. Fisk 3 and Manuel Brando 1 † Max Planck Institut f¨ ur Chemische Physik fester Stoffe, 01187 Dresden, Germany University of California, Davis, California 95616, USA University of California, Irvine, California 92697-4573, USA Abstract. We have studied the isothermal magnetization M (H) of CeCo(In 1−x Cd x ) 5 with x = 0.0075 and 0.01 down to 50 mK. Pronounced field-history dependent phe- nomena occur in the coexistence regime of the superconducting and antiferromagnetic phases. At low-fields, a phenomenological model of magnetic-flux entry well explains M (H) implying the dominance of bulk pinning effect. However, unless crystallographic quenched disorder is hysteretic, the asymmetric peak effect (ASPE) which appears at higher fields cannot be explained by the pinning of vortices due to material defects. Also the temperature dependence of the ASPE deviates from the conventional scenario for the peak effect. Comparison of our thermodynamic phase diagrams with those from previous neutron scattering and magnetoresistance experiments indicates that the pin- ning of vortices takes place at the field-history dependent antiferromagnetic domain boundaries. † Corresponding authors Email: dongjin.jang@cpfs.mpg.de, manuel.brando@cpfs.mpg.de

H – T phase diagram of YbCo2Si2 with H // [100]

We report on high-resolution dc-magnetisation (M) measurements on a single crystal of YbCo2Si2. M was measured down to 0.05 K and in fields up to 12 T, with the magnetic field H parallel to the crystallographic direction [100]. Two antiferromagnetic (AFM) phase transitions have been detected in a field ?0H = 0.1 T at TN = 1.75 K and TL = 0.9 K, in form of a sharp cusp and a sudden drop in ? = M/H, respectively. These signatures suggest that the phase transitions are 2nd order at TN and 1st order at TL. The upper transition is suppressed by a critical field ?0HN = 1.9 T. The field-dependent magnetisation shows two hysteretic metamagnetic-like steps at the lowest temperature, followed by a sharp kink, which separates the AFM region from the paramagnetic one. The magnetic H ? T phase diagram of YbCo2Si2 has been deduced from the isothermal and isofield curves. Four AFM regions were identified which are separated by 1st and 2nd order phase-transition lines.

H ? T phase diagram of YbCo2Si2 with H // [100]

We report on high-resolution dc-magnetisation (M) measurements on a single crystal of YbCo2Si2. M was measured down to 0.05 K and in fields up to 12 T, with the magnetic field H parallel to the crystallographic direction [100]. Two antiferromagnetic (AFM) phase transitions have been detected in a field ?0H = 0.1 T at TN = 1.75 K and TL = 0.9 K, in form of a sharp cusp and a sudden drop in ? = M/H, respectively. These signatures suggest that the phase transitions are 2nd order at TN and 1st order at TL. The upper transition is suppressed by a critical field ?0HN = 1.9 T. The field-dependent magnetisation shows two hysteretic metamagnetic-like steps at the lowest temperature, followed by a sharp kink, which separates the AFM region from the paramagnetic one. The magnetic H ? T phase diagram of YbCo2Si2 has been deduced from the isothermal and isofield curves. Four AFM regions were identified which are separated by 1st and 2nd order phase-transition lines.