We report a large electrocaloric effect with an adiabatic temperature change (ΔT) of 0.47 K under 20 kV cm⁻¹ combined with a broad temperature span (T_span) of 23 K within 90% ΔT (maximum) attenuation in a (Ba_0.87Ca_0.13)(Ti_0.87Hf_0.13)O₃ ceramic by indirect measurement. Here, in this (Ba_0.87Ca_0.13)(Ti_0.87Hf_0.13)O₃ ceramic, Ca²⁺ and Hf⁴⁺ are introduced into BaTiO₃ to obtain a multiphase coexisting region with a diffuse phase transition character. The large electrocaloric effect benefits from a larger number of possible equilibrium orientations of polar states due to multiphase coexistence, and the broad temperature span comes from the diffuse phase transition character. Compared to the control sample, BaTi_0.82Hf_0.18O₃ with only diffuse transition but no multiphase coexistence, (Ba_0.87Ca_0.13)(Ti_0.87Hf_0.13)O₃ displays a ΔT value nearly 1.5 times larger than that of BaTi_0.82Hf_0.18O₃ (ΔT ∼ 0.33 K), although they exhibit similar T_span values. Our work may shed light on developing high performance electrocaloric materials with broad temperature ranges.

The intrinsic magnetism has long been pursued in two-dimensional (2D) materials down to one-atomic layer thickness. But only very recently, the intrinsic magnetism of monolayer CrI₃, Fe₃GeTe₂, FePS₃, VSe₂ and bilayer Cr₂Ge₂Te₆ are verified in experiment by optical measurement, Raman spectrum and conventional magnetism measurement. Among them, the intralayer exchange interaction of FePS₃ is antiferromagnetic while all the others are ferromagnetic. Most of the ferromagnetic orders in these materials are induce by super exchange interaction. Monolayer Fe₃GeTe₂ and VSe₂ exhibit metallic character while all the others are semiconductor or insulator. Stable spontaneous magnetization can exist in these monolayer 2D materials because of their strong anisotropy. The anisotropy is mostly from the strong spin–orbit coupling of heavy atoms (CrI₃, Cr₂Ge₂Te₆, Fe₃GeTe₂). Asymmetric lattice distortion (FePS₃) or the increased density of state near Fermi level (VSe₂) may also contribute to the anisotropy. The relationship between anisotropy and stable spontaneous magnetization are discussed based on spin wave theory and Mermin-Wagner theorem. About the application, spintronics may be the most direct benefitted field. Considering the relationship between conductance and magnetic structure, the applications related with the transport property are also widely investigated. Similarly, as the coupling between spin, phonon and photon are prominent in these magnetic 2D materials, the applications based on the magnetocaloric effect and magneto-optic effect are promising. And these magnetic 2D materials may be also applied as catalyst in water-splitting or electrode of supercapacitor.

The ability to detect and analyze the state of magnetic labels with high sensitivity is of crucial importance for developing magnetic biosensors. In this work, we demonstrate for the first time, a ferromagnetic resonance (FMR) based homogeneous and volumetric biosensor for magnetic label detection. Two different isothermal amplification methods, i.e., rolling circle amplification (RCA) and loop-mediated isothermal amplification (LAMP) are adopted and combined with a standard electron paramagnetic resonance (EPR) spectrometer for FMR biosensing. For RCA-based FMR biosensor, binding of RCA products of a synthetic Vibrio cholerae target DNA sequence gives rise to the formation of aggregates of magnetic nanoparticles. Immobilization of nanoparticles within the aggregates leads to a decrease of the net anisotropy of the system and a concomitant increase of the resonance field. A limit of detection of 1 pM is obtained with a linear detection range between 7.8 and 250 pM. For LAMP-based sensing, a synthetic Zika virus target oligonucleotide is amplified and detected in 20% serum samples. Immobilization of magnetic nanoparticles is induced by their co-precipitation with Mg2P2O7 (a by-product of LAMP) and provides a detection sensitivity of 100 aM. The fast measurement, high sensitivity and miniaturization potential of the proposed FMR biosensing technology makes it a promising candidate for designing future point-of-care devices.