The realization of ferromagnetism in semiconductors is an attractive avenue for the development of spintronic applications. Here, we report a semiconducting layered metal-organic framework (MOF), namely K 3 Fe 2 [( 2,3,9,10,16,17,23,24 -octahydroxy phthalocyaninato)Fe] (K 3 Fe 2 [PcFe-O 8 ]) with spontaneous magnetization. This layered MOF features in-plane full π-d conjugation and exhibits semiconducting behavior with a room temperature carrier mobility of 15 ± 2 cm 2 V −1 s −1 as determined by time-resolved Terahertz spectroscopy. Magnetization experiments and 57 Fe Mössbauer spectroscopy demonstrate the presence of long-range magnetic correlations in K 3 Fe 2 [PcFe-O 8 ] arising from the magnetic coupling between iron centers via delocalized π electrons. The sample exhibits superparamagnetic features due to a distribution of crystal size and possesses magnetic hysteresis up to 350 K. Our work sets the stage for the development of spintronic materials exploiting magnetic MOF semiconductors.

The magnetic order of (La,Eu)2-xSrxCuO4 ( x

Topological materials ranging from topological insulators to Weyl and Dirac semimetals form one of the most exciting current fields in condensed-matter research. Many half-Heusler compounds, RPtBi (R = rare earth), have been theoretically predicted to be topological semimetals. Among various topological attributes envisaged in RPtBi, topological surface states, chiral anomaly, and planar Hall effect have been observed experimentally. Here, we report an unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide temperature range. In particular, GdPtBi exhibits an anomalous Hall conductivity of up to 60 Ω⋅cm and an anomalous Hall angle as large as 23%. Muon spin-resonance (μSR) studies of GdPtBi indicate a sharp antiferromagnetic transition () at 9 K without any noticeable magnetic correlations above Our studies indicate that Weyl points in these half-Heuslers are induced by a magnetic field via exchange splitting of the electronic bands at or near the Fermi energy, which is the source of the chiral anomaly and the AHE.

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Cerium 4f electronic spin dynamics in single crystals of the heavy-fermion system CeFePO is studied by means of ac-susceptibility, specific heat and muon-spin relaxation (µSR). Short-range static magnetism occurs below the freezing temperature Tg ≈ 0.7 K, which prevents the system from accessing the putative ferromagnetic quantum critical point. In the µSR, the sample-averaged muon asymmetry function is dominated by strongly inhomogeneous spin fluctuations below 10 K and exhibits a characteristic time-field scaling relation expected from glassy spin dynamics, strongly evidencing cooperative and critical spin fluctuations. The overall behavior can be ascribed neither to canonical spin glasses nor other disorder-driven mechanisms.PACS numbers: 71.27.+a, 64.70.Tg, 76.75.+i, 75.50.Lk A long-standing question in the field of quantum criticality is whether a ferromagnetic (FM) quantum critical point (QCP) generally exists and, if not, which are the possible ground states of matter that replace it. Quantum critical points occur when a material is continuously tuned with an external parameter (pressure, magnetic field, etc.) between competing ground states at zero temperature [1, 2]. An FM-QCP then exists when it is possible to shift the Curie transition temperature T C of a ferromagnet continuously to zero where a second order quantum phase transition takes place. Quantum phase transitions occur at zero entropy and are driven by quantum rather than thermal fluctuations. These fluctuations diverge at the QCP modifying the excitation spectrum of a metal and leading to a fundamental instability of Landau's Fermi liquid (FL) [3]. Typical signatures of such a behavior are observed in magnetic, thermal and transport properties and are referred to as non-Fermi-liquid (NFL) phenomena [4].Although there is clear evidence for the existence of antiferromagnetic (AFM) QCPs, the FM-QCP case is controversial. In recent years, substantial experimental and theoretical efforts were made to further investigate this problem. However, a wide range of possibilities exists. On theoretical grounds, a 3-dimensional (3D) FM-QCP is believed to be inherently unstable, either towards a first order phase transition or towards an inhomogeneous magnetic phase (modulated/textured structures) [5][6][7]. Similar results have been obtained in 2D [5,8,9] CeRuPO [21] where the FM transition temperature is suppressed to T = 0 by hydrostatic pressure, exhibit a change into AFM order before reaching the QCP. There are Ce-based alloys (CePd 1−x Rh x [22]) and also d-electron metals (Ni 1−x V x [23]) where it seems that local disorder-driven mechanisms such as Kondo disorder or the quantum Griffiths phase (QGP) scenario are responsible for the NFL properties [24][25][26]. Broad and strongly T dependent NMR and µSR linewidths are indicative for such disorder-driven mechanisms. As a consequence spin-glass-like behavior is often found, e.g., in CePd 1−x Rh x , and power-law corrections to the thermodynamic and transport properties as well as in the local spi...