501 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
Scaling of the magnetic entropy and magnetization in YbRh_2(Si_{0.95}Ge_{0.05})_2
The magnetic entropy of YbRh_2(Si_{0.95}Ge_{0.05})_2 is derived from
low-temperature ( mK) specific heat measurements. Upon field-tuning
the system to its antiferromagnetic quantum critical point unique temperature
over magnetic field scaling is observed indicating the disintegration of heavy
quasiparticles. The field dependence of the entropy equals the temperature
dependence of the dc-magnetization as expected from the Maxwell relation. This
proves that the quantum-critical fluctuations affect the thermal and magnetic
properties in a consistent way.Comment: 6 pages, 2 figures, manuscript submitted to SCES2004 conferenc
Coexistence of Superconductivity and Antiferromagnetism in Multilayered High- Superconductor HgBaCaCuO: A Cu-NMR Study
We report a coexistence of superconductivity and antiferromagnetism in
five-layered compound HgBaCaCuO (Hg-1245) with K,
which is composed of two types of CuO planes in a unit cell; three inner
planes (IP's) and two outer planes (OP's). The Cu-NMR study has revealed that
the optimallydoped OP undergoes a superconducting (SC) transition at
K, whereas the three underdoped IP's do an antiferromagnetic (AF) transition
below 60 K with the Cu moments of . Thus bulk
superconductivity with a high value of K and a static AF ordering at
K are realized in the alternating AF and SC layers. The AF-spin
polarization at the IP is found to induce the Cu moments of at
the SC OP, which is the AF proximity effect into the SC OP.Comment: 6 pages, 8 figure
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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