561 research outputs found
Uniform Mixing of High-Tc Superconductivity and Antiferromagnetism on a Single CuO2 Plane in Hg-based Five-layered Cuprate
We report a site selective Cu-NMR study on under-doped Hg-based five-layered
high- cuprate HgBa2Ca4Cu5Oy with a Tc=72 K. Antiferromagnetism (AF)
has been found to take place at TN=290 K, exhibiting a large antiferromagnetic
moment of 0.67-0.69uB at three inner planes (IP's). This value is comparable to
the values reported for non-doped cuprates, suggesting that the IP may be in a
nearly non-doped regime. Most surprisingly, the AF order is also detected with
M(OP)=0.1uB even at two outer planes (OP's) that are responsible for the onset
of superconductivity (SC). The high-Tc SC at Tc = 72 K can uniformly coexist on
a microscopic level with the AF at OP's. This is the first microscopic evidence
for the uniform mixed phase of AF and SC on a single CuO2 plane in a simple
environment without any vortex lattice and/or stripe order.Comment: 4 pages, 4 figures. To be published in Phys.Rev.Let
Gapped ground state in the zigzag pseudospin-1/2 quantum antiferromagnetic chain compound PrTiNbO6
We report a single-crystal study on the magnetism of the rare-earth compound
PrTiNbO that experimentally realizes the zigzag pseudospin-
quantum antiferromagnetic chain model. Random crystal electric field caused by
the site mixing between non-magnetic Ti and Nb, results in the
non-Kramers ground state quasi-doublet of Pr with the effective
pseudospin- Ising moment. Despite the antiferromagnetic intersite
coupling of about 4 K, no magnetic freezing is detected down to 0.1 K, whilst
the system approaches its ground state with almost zero residual spin entropy.
At low temperatures, a sizable gap of about 1 K is observed in zero field. We
ascribe this gap to off-diagonal anisotropy terms in the pseudospin
Hamiltonian, and argue that rare-earth oxides open an interesting venue for
studying magnetism of quantum spin chains.Comment: 11 pages, 10 figures, 1D correlated magnetism of non-Kramers Ising
quasi-doublets in PrTiNbO
Low Temperature Thermodynamic Properties of the Heavy Fermion Compound YbAgGe Close to the Field-Induced Quantum Critical Point
We present temperature and field dependent heat capacity and magnetization
data taken at temperatures down to 50 mK and in an applied magnetic field up to
11.5 Tesla for YbAgGe, a heavy-fermion compound with a field induced quantum
critical point. These data clearly indicate that the same electronic degrees of
freedom are responsible for the features seen in both specific heat and
magnetization data. In addition, they further refine the different boundaries
suggested for the H - T phase diagram of YbAgGe through previous,
magneto-transport measurements, and allow for further understanding of
different phases on the H - T phase diagram, in particular, clearly
disconnecting the field-induced quantum critical point in YbAgGe from any sort
of saturation of the Yb moment in higher applied magnetic field
Full-gap superconductivity robust against disorder in heavy-fermion CeCu2Si2
A key aspect of unconventional pairing by the antiferromagnetic
spin-fluctuation mechanism is that the superconducting energy gap must have
opposite sign on different parts of the Fermi surface. Recent observations of
non-nodal gap structure in the heavy-fermion superconductor CeCuSi were
then very surprising, given that this material has long been considered a
prototypical example of a superconductor where the Cooper pairing is
magnetically mediated. Here we present a study of the effect of controlled
point defects, introduced by electron irradiation, on the temperature-dependent
magnetic penetration depth in CeCuSi. We find that the
fully-gapped state is robust against disorder, demonstrating that low-energy
bound states, expected for sign-changing gap structures, are not induced by
nonmagnetic impurities. This provides bulk evidence for -wave
superconductivity without sign reversal.Comment: 5 pages, 4 figures + Supplemental Material (1 page, 1 figure). Will
appear in Phys. Rev. Let
Frustrated magnet for adiabatic demagnetization cooling to milli-Kelvin temperatures
Generation of very low temperatures has been crucially important for
applications and fundamental research, as low-temperature quantum coherence
enables operation of quantum computers and formation of exotic quantum states,
such as superfluidity and superconductivity. One of the major techniques to
reach milli-Kelvin temperatures is adiabatic demagnetization refrigeration
(ADR). This method uses almost non-interacting magnetic moments of paramagnetic
salts where large distances suppress interactions between the magnetic ions.
The large spatial separations are facilitated by water molecules, with a
drawback of reduced stability of the material. Here, we show that an
HO-free frustrated magnet KBaYb(BO) can be ideal refrigerant for
ADR, achieving at least 22\,mK upon demagnetization under adiabatic conditions.
Compared to conventional refrigerants, KBaYb(BO does not degrade even
under high temperatures and ultra-high vacuum conditions. Further, its
frustrated magnetic network and structural randomness enable cooling to
temperatures several times lower than the energy scale of magnetic
interactions, which is the main limiting factor for the base temperature of
conventional refrigerants.Comment: accepted for publication in Communications Material
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