The semiconducting properties of most 2D magnets investigated so far, however, are strongly affected by the extremely narrow widths of their conduction and valence bands, typically a few tens of meV or less. [7][8][9][10][11][12][13] Such narrow bandwidths cause electron localization and prevent low-temperature conductivity measurements, which is why transport experiments probing the magnetic properties of 2D semiconductors have been so far limited to studies of tunneling through atomically thin multilayer barriers. [14][15][16][17][18][19][20][21] CrSBr [22] (see Figure 1a)-a recently introduced 2D magnetic semiconductor-appears to be an exception. [23,24] First-principles calculations (shown in Figure 1b) predict its conduction band to have a width of ≈1.5 eV. [24,25] Accordingly, low-temperature in-plane magnetoresistance measurements (see Figure 1c,d) could be performed successfully, and analyzed to determine the magnetic phase diagram. [23] The unique magnetic properties of this material have been further showcased by experiments on van der Waals (vdW) interfaces, in which CrSBr was found to imprint into an adjacent graphene layer a giant exchange interaction, much stronger than what has been reported in earlier work on analogous heterostructures. [26] Electronic transport through exfoliated multilayers of CrSBr, a 2D semiconductor of interest because of its magnetic properties, is investigated. An extremely pronounced anisotropy manifesting itself in qualitative and quantitative differences of all quantities measured along the in-plane a and b crystallographic directions is found. In particular, a qualitatively different dependence of the conductivities σ a and σ b on temperature and gate voltage, accompanied by orders of magnitude differences in their values (σ b /σ a ≈ 3 × 10 2 to 10 5 at low temperature and negative gate voltage) are observed, together with a different behavior of the longitudinal magnetoresistance in the two directions and the complete absence of the Hall effect in transverse resistance measurements. These observations appear not to be compatible with a description in terms of conventional band transport of a 2D doped semiconductor. The observed phenomenology-and unambiguous signatures of a 1D van Hove singularity detected in energy-resolved photocurrent measurements-indicate that electronic transport through CrSBr multilayers is better interpreted by considering the system as formed by weakly and incoherently coupled 1D wires, than by conventional 2D band transport. It is concluded that CrSBr is the first 2D semiconductor to show distinctly quasi-1D electronic transport properties.

The van-der-Waals material CrSBr stands out as a promising two-dimensional magnet. Here, we report on its detailed magnetic and structural characteristics. We evidence that it undergoes a transition to an A-type antiferromagnetic state below TN ≈ 140 K with a pronounced two-dimensional character, preceded by ferromagnetic correlations within the monolayers. Furthermore, we unravel the low-temperature hidden-order within the long-range magnetically-ordered state. We find that it is associated to a slowing down of the magnetic fluctuations, accompanied by a continuous reorientation of the internal field. These take place upon cooling below Ts ≈ 100 K, until a spin freezing process occurs at T* ≈ 40 K. We argue this complex behavior to reflect a crossover driven by the in-plane uniaxial anisotropy, which is ultimately caused by its mixed-anion character. Our findings reinforce CrSBr as an important candidate for devices in the emergent field of two-dimensional magnetic materials.

Ozone oxidation has allowed the stabilization of a very high iron oxidation state in the FeSr 2 YCu 2 O 7.85 cuprate, in which a long-range magnetic ordering of the high valent iron cations coexists with the superconducting interactions (magnetic ordering temperature T N = 110 K > superconducting critical temperature T c = 70 K). The somewhat unexpected A-type AFM structure, with a μ(Fe) ∼ 2 μ B magnetic saturation moment associated with the hypervalent iron sublattice, suggests an unusual low spin state for the iron cations, while the low dimensionality of the magnetic structure results in a soft switching toward ferromagnetism under small external magnetic fields. The role of the crystal structure and of the high charge concentration in the stabilization of this unusual electronic configuration for the iron cations is discussed.

Low-temperature reaction of A-site-ordered layered perovskite Eu 2 SrFe 2 O 7 (T structure) with CaH 2 induces a shift in the Eu 2 O 2 slabs to form Eu 2 SrFe 2 O 6 with a T′ structure (I4/mmm space group) in which only the Fe cation is reduced. Contrary to the previously reported T′ structures with Jahn−Teller-active d 9 cations (Cu 2+ and Ni + ), stabilization of Eu 2 SrFe 2 O 6 with the Fe 2+ (d 6 ) cation reflects the stability of the FeO 4 square-planar unit. The stability of T′-type Eu 2 SrFe 2 O 6 over a T-type polymorph is confirmed by density functional theory calculations, revealing the d z 2 occupancy for the T′ structure. Eu 2 SrFe 2 O 6 has a bilayer magnetic framework with an Fe−O−Fe superexchange J ∥ and an Fe−Fe direct exchange J ⊥ (where J ∥ > J ⊥ ), which broadly explains the observed T N of 390− 404 K. Interestingly, the magnetic moments of Eu 2 SrFe 2 O 6 lie in the ab plane, in contrast to the structurally similar Sr 3 Fe 2 O 4 Cl 2 having an out-of-plane spin alignment.