Multilayered cuprates possess not only the highest superconducting temperature transition but also offer a unique platform to study disorder-free CuO2 planes and the interplay between competing orders with superconductivity. Here, we study the underdoped trilayer cuprate HgBa2Ca2Cu3O8+δ and we report quantum oscillation and Hall effect measurements in magnetic field up to 88 T. A careful analysis of the complex spectra of quantum oscillations strongly supports the coexistence of an antiferromagnetic order in the inner plane and a charge order in the outer planes. The presence of an ordered antiferromagnetic metallic state that extends deep in the superconducting phase is a key ingredient that supports magnetically mediated pairing interaction in cuprates.

HgBa2Ca2Cu3O8+δ V. Oliviero1,†, S. Benhabib1,†,‡,∗, I. Gilmutdinov, B. Vignolle, L. Drigo , M. Massoudzadegan, M. Leroux, G.L.J.A. Rikken, A. Forget, D. Colson, D. Vignolles1,∗ and C. Proust1,∗ LNCMI-EMFL, CNRS UPR3228, Univ. Grenoble Alpes, Univ. Toulouse, INSA-T, Grenoble and Toulouse, France Institut de Chimie de la Matière Condensée, Bordeaux, France Service de Physique de l’Etat Condensé, CEA Saclay (CNRS-URA 2464), Gif sur Yvette 91191, France

AbstractSpinel is a ubiquitous mineral in mafic/ultramafic rocks. Spinel cores chemistry is extensively used as a petrogenetic proxy while their alteration phases, ferritchromite, and Cr‐magnetite, are used as metamorphic grade indicators. However, the magnetic properties and composition of these phases are still ill‐defined and no consensus exists concerning the metamorphic conditions involved in their formation. Here, we use the magnetic properties of these Cr‐spinel alteration phases, via field‐dependent parameters and observations with a magnetic microscope coupled with mineral chemistry and Mössbauer spectroscopy, to better constrain their composition. We identify Cr‐magnetite by a Curie point of ca. 520°C. We show that it is characterized by an n between 0.1 and 0.2 in the Fe‐Cr spinel formula [Fe2+(Fe1−nCrn)2O4], which corresponds to 6–13 wt.% of Cr2O3. The abundance of Cr‐magnetite indicates a strong alteration of Cr‐spinels that could reflect a significant hydrothermal activity rather than a high metamorphism grade. Normalized variation curves of the magnetic susceptibility during heating allow a relative quantification of the contributions of different magnetic phases to the magnetic susceptibility. This highlights a link between ferritchromite destabilization into maghemite at ca. 130°C followed by the destabilization of this maghemite starting at 300°C. We identify specific covariation trends between these two magnetic species characterizing different alteration processes. This study opens the door to magnetic monitoring of the Cr‐spinel alteration state in mafic and ultramafic rocks. It constitutes a new, fast, and weakly destructive way to study the petrological history of both terrestrial and extraterrestrial rocks.

We present upper critical magnetic fields data for κ(BEDT-TTF) 2 Cu[N(CN) 2 ]Br (hereafter k-Br), single crystals with the magnetic field applied either or perpendicular and parallel to the conducting layers. The H-T phase diagram in these single crystals has been deduced from tunnel diode oscillator-based contactless measurements in pulsed magnetic fields up to 56 T for the inter-plane ( H ∥ b) and in-plane ( H ∥ ac) field directions. Temperature dependence of the magnetic penetration depth in DC fields is also reported. The temperature dependence of the upper critical magnetic field H c2 ( T ) is not accounted for the Werthamer-Helfand-Hohenberg model for in-plane configuration. For the inter-plane orientation, a significant upward curvature is observed as the temperature decreases, in the range close to T c , followed by saturation at lower temperatures. Possibly, this upturn is an indication of flux-line lattice melting.

We have synthesized heterostructures that consist of a layer of a cuprate insulator, La2CuO4, and a layer of a nonsuperconducting cuprate metal, La1.55Sr0.45CuO4. Such bilayers show high-T-c interface superconductivity confined within a single CuO2 plane. Here, we explore the behavior of interface superconductivity at high frequencies (up to 50 MHz) under high magnetic fields (up to 56 T). We find that interface superconductivity persists up to very high perpendicular fields (exceeding 40 T). The critical magnetic field H-m(T) shows an upward divergence with decreasing temperature suggestive of vortex-lattice melting, similar to what is observed in bulk superconducting cuprates.

Heterostructures made of a layer of a cuprate insulator La2CuO4 on the top of a layer of a nonsuperconducting cuprate metal La1.55Sr0.45CuO4 show high-T-c interface superconductivity confined within a single CuO2 plane. Given this extreme quasi-two-dimensional quantum confinement, it is of interest to find out how interface superconductivity behaves when exposed to an external magnetic field. With this motivation, we have performed contactless tunnel-diode-oscillator-based measurements in pulsed magnetic fields up to 56 T as well as measurements of the complex mutual inductance between a spiral coil and the film in static fields up to 3 T. Remarkably, we observe that interface superconductivity survives up to very high perpendicular fields, in excess of 40 T. In addition, the critical magnetic field H-m (T) reveals an upward divergence with decreasing temperature, in line with vortex melting as in bulk superconducting cuprates.

Cd(3)As(2) is a candidate three-dimensional Dirac semimetal which has exceedingly high mobility and nonsaturating linear magnetoresistance that may be relevant for future practical applications. We report magnetotransport and tunnel diode oscillation measurements on Cd(3)As(2), in magnetic fields up to 65 T and temperatures between 1.5 and 300 K. We find that the nonsaturating linear magnetoresistance persists up to 65 T and it is likely caused by disorder effects, as it scales with the high mobility rather than directly linked to Fermi surface changes even when approaching the quantum limit. From the observed quantum oscillations, we determine the bulk three-dimensional Fermi surface having signatures of Dirac behavior with a nontrivial Berry phase shift, very light effective quasiparticle masses, and clear deviations from the band-structure predictions. In very high fields we also detect signatures of large Zeeman spin splitting (g∼16).

Temperature dependence of the upper critical magnetic field (Hc2) of single crystalline FeTe0.5Se0.5 (Tc = 14.5 K) have been determined by tunnel diode oscillator-based measurements in magnetic fields of up to 55 T and temperatures down to 1.6 K. The Werthamer-Helfand-Hohenberg model accounts for the data for magnetic field applied both parallel (H || ab) and perpendicular (H || c) to the iron conducting plane, in line with a single band superconductivity. Whereas Pauli pair breaking is negligible for H || c, Pauli contribution is evidenced for H || ab with Maki parameter alpha= 1.4, corresponding to Pauli field HP = 79 T. As a result, the Hc2 anisotropy (= Habc2 /Hcc2) which is already rather small at Tc (gamma = 1.6) further decreases as the temperature decreases and becomes smaller than 1 at liquid helium temperatures.

We present measurements of the resistivity $\rho_{x,x}$ of URu2Si2 high-quality single crystals in pulsed high magnetic fields up to 81~T at a temperature of 1.4~K and up to 60~T at temperatures down to 100~mK. For a field \textbf{H} applied along the magnetic easy-axis \textbf{c}, a strong sample-dependence of the low-temperature resistivity in the hidden-order phase is attributed to a high carrier mobility. The interplay between the magnetic and orbital properties is emphasized by the angle-dependence of the phase diagram, where magnetic transition fields and crossover fields related to the Fermi surface properties follow a 1/$\cos\theta$-law, $\theta$ being the angle between \textbf{H} and \textbf{c}. For $\mathbf{H}\parallel\mathbf{c}$, a crossover defined at a kink of $\rho_{x,x}$, as initially reported in [Shishido et al., Phys. Rev. Lett. \textbf{102}, 156403 (2009)], is found to be strongly sample-dependent: its characteristic field $\mu_0H^*$ varies from $\simeq20$~T in our best sample with a residual resistivity ratio RRR of $225$ to $\simeq25$~T in a sample with a RRR of $90$. A second crossover is defined at the maximum of $\rho_{x,x}$ at the sample-independent characteristic field $\mu_0H_{\rho,max}^{LT}\simeq30$~T. Fourier analyzes of SdH oscillations show that $H_{\rho,max}^{LT}$ coincides with a sudden modification of the Fermi surface, while $H^*$ lies in a regime where the Fermi surface is smoothly modified. For $\mathbf{H}\parallel\mathbf{a}$, i) no phase transition is observed at low temperature and the system remains in the hidden-order phase up to 81~T, ii) quantum oscillations surviving up to 7~K are related to a new and almost-spherical orbit - for the first time observed here - at the frequency $F_\lambda\simeq1400$~T and associated with a low effective mass $m^*_\lambda=(1\pm0.5)\cdot m_0$, and iii) no Fermi surface modification occurs up to 81~T.

We report a high magnetic field study up to 55 T of the nearly optimally doped iron-pnictide superconductor Ca_10(Pt_3As_8) ((Fe_1-xPt_x)_2As_2)_5 (x=0.078(6)) with a Tc 10 K using magnetic torque, tunnel diode oscillator technique and transport measurements. We determine the superconducting phase diagram, revealing an anisotropy of the irreversibility field up to a factor of 10 near Tc and signatures of multiband superconductivity. Unexpectedly, we find a spin-flop like anomaly in magnetic torque at 22 T, when the magnetic field is applied perpendicular to the ab planes, which becomes significantly more pronounced as the temperature is lowered to 0.33 K. As our superconducting sample lies well outside the antiferromagnetic region of the phase diagram, the observed field-induced transition in torque indicates a spin-flop transition not of long-range ordered moments, but of nematic-like antiferromagnetic fluctuations.

M. D. Watson,1 A. McCollam,2 S. F. Blake,1 D. Vignolles,3 L. Drigo,3 I. I. Mazin,4 D. Guterding,5 H. O. Jeschke,5 R. Valentı́,5 N. Ni,6,7,8 R. Cava,8 and A. I. Coldea1,* 1Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kindom 2High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands 3Laboratoire National des Champs Magnétiques Intenses (CNRS, INSA, UJF, UPS), Toulouse, France 4Code 6393, Naval Research Laboratory, Washington, DC 20375, USA 5Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany 6Department of Physics and Astronomy University of California, Los Angeles, USA 7Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 8Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA (Received 15 October 2013; revised manuscript received 26 April 2014; published 30 May 2014)

The H-T phase diagrams of single crystalline electron-doped K0.83Fe1.83Se2 (KFS1), K0.8Fe2Se2 (KFS2) and hole-doped Eu0.5K0.5Fe2As2 (EKFA) have been deduced from tunnel diode oscillator-based contactless measurements in pulsed magnetic fields up to 57 T for the interplane (H parallel to c) and in-plane (H parallel to ab) directions. The temperature dependence of the upper critical magnetic field H-c2(T) relevant to EFKA is accounted for by Pauli model including an anisotropic Pauli paramagnetic contribution (mu H-B(p) = 114 T for H parallel to ab and 86 T for H parallel to c). This is also the case of KFS1 and KFS2 for H parallel to ab whereas a significant upward curvature, accounted for by a two-gap model, is observed for H parallel to c. Despite the presence of antiferromagnetic lattice order within the superconducting state of the studied compounds, no influence of magnetic ordering on the temperature dependence of H-c2(T) is observed. DOI: 10.1103/PhysRevB.87.094508

Analytical formulae for de Haas-van Alphen (dHvA) oscillations in linear chain of coupled two-dimensional (2D) orbits (Pippard's model) are derived systematically taking into account the chemical potential oscillations in magnetic field. Although corrective terms are observed, basic (alpha) and magnetic-breakdown-induced (beta and 2 beta - alpha) orbits can be accounted for by the Lifshits-Kosevich (LK) and Falicov-Stachowiak semiclassical models in the explored field and temperature ranges. In contrast, the "forbidden orbit" beta - alpha amplitude is described by a non-LK equation involving a product of two classical orbit amplitudes. Furthermore, strongly non-monotonic field and temperature dependence may be observed for the second harmonics of basic frequencies such as 2 alpha and the magnetic breakdown orbit beta + alpha, depending on the value of the spin damping factors. These features are in agreement with the dHvA oscillation spectra of the strongly 2D organic metal theta-(ET)(4)CoBr4(C6H4Cl2).

We present a novel approach for terahertz time-domain spectroscopy of magneto-optic phenomena. The setup used in this work combines a tabletop pulsed magnet and a standard terahertz time-domain spectroscopy system. The approach is based on repetitive operation of the pulsed magnet and step-wise increment of the delay time of the time-domain spectroscopy system. The method is demonstrated by plotting the magneto-transmission spectra of linearly polarized THz pulses through the hole gas of a Ge sample and the electron gas of GaAs, InSb and InAs samples. Cyclotron resonance spectra are displayed in the frequency range from 200 GHz to 2 THz and for a magnetic field up to 6 T. The GaAs spectra are analyzed in more detail using simulations based on the Drude model.

We report measurements of the temperature dependence of the radio frequency magnetic penetration depth in Ba0.68K0.32Fe2As2 and Ba(Fe0.93Co0.07)2As2 single crystals in pulsed magnetic fields up to 60 T. From our data, we construct an H-T-phase diagram for the inter-plane (H ‖ c) and in-plane (H ‖ ab) directions for both compounds. For both field orientations in Ba0.68K0.32Fe2As2 we find a concave curvature of the H c2(T) lines with decreasing anisotropy and saturation towards lower temperature. Taking into account Pauli spin paramagnetism we can describe H c2(T) and its anisotropy. In contrast, we find that Pauli paramagnetic pair breaking is not essential for Ba(Fe0.93Co0.07)2As2. For this electron-doped compound, the data support a H c2(T) dependence that can be described by the Werthamer-Helfand-Hohenberg model for H ‖ ab and a two-gap behavior for H ‖ c.

Analytical formulae for de Haas-van Alphen (dHvA) oscillations in linear chain of coupled two-dimensional (2D) orbits (Pippard's model) are derived systematically taking into account the chemical potential oscillations in magnetic field. Although corrective terms are observed, basic (α) and magnetic-breakdown–induced (β and 2β−α) orbits can be accounted for by the Lifshits-Kosevich (LK) and Falicov-Stachowiak semiclassical models in the explored field and temperature ranges. In contrast, the “forbidden orbit”β−α amplitude is described by a non-LK equation involving a product of two classical orbit amplitudes. Furthermore, strongly non-monotonic field and temperature dependence may be observed for the second harmonics of basic frequencies such as 2α and the magnetic breakdown orbit β+α, depending on the value of the spin damping factors. These features are in agreement with the dHvA oscillation spectra of the strongly 2D organic metal θ-(ET)4CoBr4(C6H4Cl2).

Tunnel diode oscillator-based technique has been used for quantum oscillations spectra determination of a quasi-two dimensional organic metal in pulsed high magnetic fields of up to 55 T. It is demonstrated that reliable field-dependent quantitative data can be obtained in the case of complex oscillatory spectra provided adequate data processing is conducted.