A. A. Aczel

Li(Zn,Mn)As as a new generation ferromagnet based on a I–II–V semiconductor

In a prototypical ferromagnet (Ga,Mn)As based on a III-V semiconductor, substitution of divalent Mn atoms into trivalent Ga sites leads to severely limited chemical solubility and metastable specimens available only as thin films. The doping of hole carriers via (Ga,Mn) substitution also prohibits electron doping. To overcome these difficulties, Masek et al. theoretically proposed systems based on a I-II-V semiconductor LiZnAs, where isovalent (Zn,Mn) substitution is decoupled from carrier doping with excess/deficient Li concentrations. Here we show successful synthesis of Li(1+y)(Zn(1-x)Mn(x))As in bulk materials. Ferromagnetism with a critical temperature of up to 50 K is observed in nominally Li-excess (y=0.05-0.2) compounds with Mn concentrations of x=0.02-0.15, which have p-type metallic carriers. This is presumably due to excess Li in substitutional Zn sites. Semiconducting LiZnAs, ferromagnetic Li(Zn,Mn)As, antiferromagnetic LiMnAs, and superconducting LiFeAs systems share square lattice As layers, which may enable development of novel junction devices in the future.

Absence of superconductivity in single-phase CaFe2As2 under hydrostatic pressure

Recent high-pressure studies found that structural/magnetic phase transitions are very pressure sensitive in

Phase separation and suppression of critical dynamics at quantum phase transitions of MnSi and (Sr 1−x Ca x )RuO 3

{\text{CaFe}}_{2}{\text{As}}_{2}

Superconducting state coexisting with a phase-separated static magnetic order in (Ba,K)Fe2As2, (Sr,Na)Fe2As2, and CaFe2As2

and that superconductivity can be achieved under modest pressure, although details of the sharpness and temperature of transitions vary between liquid medium and gas medium measurements. To better understand this issue, we performed high-pressure susceptibility and transport studies on

Muon-spin-relaxation studies of magnetic order and superfluid density in antiferromagnetic NdFeAsO, BaFe2As2, and superconducting Ba1-xKxFe2As2

{\text{CaFe}}_{2}{\text{As}}_{2}

Magnetic properties of the geometrically frustrated S= 1 2 antiferromagnets, La2 LiMoO6 and Ba2 YMoO 6, with the B-site ordered double perovskite structure: Evidence for a collective spin-singlet ground state

, using helium as the pressure medium. The signatures of the transitions to the low-temperature orthorhombic and collapsed tetragonal phases remained exceptionally sharp, and no signature of bulk superconductivity was found under our hydrostatic conditions. Our results suggest that superconductivity in

Spin ice: magnetic excitations without monopole signatures using muon spin rotation.

{\text{CaFe}}_{2}{\text{As}}_{2}

Field-induced Bose-Einstein condensation of triplons up to 8 K in Sr3Cr2O8.

is associated with a low-temperature, multicrystallographic-phase sample that is the result of nonhydrostatic conditions associated with the combination of a first-order structural phase transition and frozen liquid media.

Magnetic order and ice rules in the multiferroic spinel FeV 2 O 4

Phase separation and suppression of critical dynamics at quantum phase transitions of MnSi and (Sr 1− x Ca x )RuO 3

Muon spin rotation measurement of the magnetic field penetration depth in Ba ( Fe 0.926 Co 0.074 ) 2 As 2 : Evidence for multiple superconducting gaps

By muon spin-relaxation measurements on single-crystal specimens, we show that superconductivity in the AFe(2)As(2) (A=Ca,Ba,Sr) systems, in both the cases of composition and pressure tunings, coexists with a strong static magnetic order in a partial volume fraction. The superfluid response from the remaining paramagnetic volume fraction of (Ba0.5K0.5)Fe2As2 exhibits a nearly linear variation in T at low temperatures, suggesting an anisotropic energy gap with line nodes and/or multigap effects. .