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Cyclic 3d-4f molecular magnets have received considerable attention owing to their potential applications in high-density data storage and quantum information processing. As a rare example of ferromagnetic polynuclear Cr rings, {Cr8Y8} represents a valuable test bed to directly study the magnetic interaction between Cr3+ ions in large hexadecametallic {Cr8Ln8} (Ln = 4f metal) molecules. We have proposed a "single-J" model to approximate the low-temperature spin dynamics of {Cr8Y8} in our earlier study, while a zero-field splitting (ZFS) of the quantum levels was also suggested by the heat capacity data. In order to have a deeper understanding of the magnetism of {Cr8Y8}, it is necessary to verify the ZFS by means of high-resolution spectral methods and identify its origin. In this work, we present a high-frequency electron spin resonance (HF-ESR) study on the ZFS of {Cr8Y8}. The X-band ESR spectra consists of multi-peak structure, indicative of magnetic anisotropy that breaks the degeneracy between spin states in the absence of a magnetic field. HF-ESR spectra are collected to extract the ZFS parameters. We observed a sharp resonance peak due to the transitions between the S = 11 quantum levels and a broadband corresponding to a distribution of resonance peaks due to the ZFS of the S = 12 quantum levels. By analyzing HF-ESR spectra, we confirm the expected S = 12 ground state and determine its ZFS parameter D as −0.069 K, and, furthermore, we reproduce the spectra recorded at 154 GHz. The macrospin model proves to still be valid. The ZFS is attributed to the axial magnetic anisotropy, as found in some other Cr-based molecular wheels. The detailed HF-ESR investigation presented in this paper will benefit the studies on other {Cr8Ln8} wheels with magnetic Ln3+ ions and highlights the importance of the HF-ESR method as a high-resolution probe in determining the ZFS parameters with very small magnitude. [ABSTRACT FROM AUTHOR]

A chiral soliton lattice (CSL) is a topological spin-texture that has potential applications in next-generation spintronic devices. In this work, we performed angle-dependence of magnetization and electron spin resonance (ESR) investigations on the CSL host Yb(Ni1−xCux)3Al9 with x = 0.06 (YNCA). The angle-dependent magnetization reveals a peculiar variable magnetic anisotropy. The maximum magnetization axis is parallel to the ab-plane below the field of ∼35.7 kOe while shifts to the c-axis at higher fields. The microwave responses of the CSL helicoid and ferromagnetic resonance (FMR) of the forced ferromagnetic state (FFM) are observed and appear as two resonance lines on ESR spectra with the highest intensities in the ab-plane. When the external field is rotated from H ⊥ c to H / / c , the resonance field H r 1 corresponding to the CSL helicoid decreases while H r 2 correlated with the FMR increases. Furthermore, the temperature-dependent ESR shows that the CSL persists until 15 K much higher than TC (6.4 K), which suggests a precursor phenomenon. The microwave response in YNCA provides a powerful tool for modulating and researching the CSL. [ABSTRACT FROM AUTHOR]

Spin-orbit coupled honeycomb magnets with the Kitaev interaction have received a lot of attention due to their potential of hosting exotic quantum states including quantum spin liquids. Thus far, the most studied Kitaev systems are 4d/5d-based honeycomb magnets. Recent theoretical studies predicted that 3d-based honeycomb magnets, including Na2Co2TeO6 (NCTO), could also be a potential Kitaev system. Here, we have used a combination of heat capacity, magnetization, electron spin resonance measurements alongside inelastic neutron scattering (INS) to study NCTO's quantum magnetism, and we have found a field-induced spin disordered state in an applied magnetic field range of 7.5 T < B (⊥ b-axis) < 10.5 T. The INS spectra were also simulated to tentatively extract the exchange interactions. As a 3d-magnet with a field-induced disordered state on an effective spin-1/2 honeycomb lattice, NCTO expands the Kitaev model to 3d compounds, promoting further interests on the spin-orbital effect in quantum magnets. The honeycomb lattice with a spin-orbit interaction can give rise to exotic quantum states. With the measurements of bulk properties and inelastic neutron scattering, Lin et al demonstrate the existence of a field induced spin-disordered state in Na2Co2TeO6 and extend the Kitaev model to 3d system. [ABSTRACT FROM AUTHOR]

We report a comprehensive investigation of the frustrated magnetism on the delafossite oxides, α-CrOOH and α-CrOOD, which experimentally realize the S = 3/2 nearly-Heisenberg antiferromagnetic (J1 > 0) model on a triangular lattice with weak single-ion anisotropy (D). The electron spin resonance (ESR), neutron scattering, and specific heat (Cm) measurements on both α-CrOOH and α-CrOOD consistently indicate that the long-range 120° Néel order is significantly suppressed and both systems are in the vicinity of a spin-liquid phase with Cm ∼ T2 at low temperatures. The strength of D is quantitatively determined from fitting the high-temperature ESR linewidth and magnetic susceptibility, and its minus sign (D < 0, easy-axis type) is suggested by the low-energy (E ⩽ 2 meV) spin excitations. This easy-axis anisotropy (D/J1 ∼ −5%) competes with the 120° Néel order and thus enhances the quantum spin fluctuations at low temperatures. [ABSTRACT FROM AUTHOR]

While charge-ordering transition is well established in the oxygen-deficient layered cobaltite YBaCo2O5, there has been no evidence for the transition in the analogous compound GdBaCo2O5 either from neutron diffraction or from magnetic susceptibility experiments. In this paper, we present comparative studies on the electron spin resonance (ESR) of Gd3+ ions in Y1-xGdxBaCo2O5 (x = 0.01, 0.25, and 1) polycrystalline samples. Magnetic susceptibility was also performed for comparison with the ESR results. It was found that charge-ordering transition for Y0.75Gd0.25BaCo2O5 revealed by the susceptibility is also manifested in the characters of the ESR data. The similar temperature-evolution of the ESR parameters for GdBaCo2O5 provides a support for the existence of charge-ordering transition, although no characteristic of the transition is evidenced from susceptibility experiments, which can be understood as being hidden by dominant paramagnetism of Gd3+ ions in this compound. We have interpreted the temperature variation of ESR parameters in terms of electron localization associated with Co2+/Co3+ charge ordering. [ABSTRACT FROM AUTHOR]

Gd-doped Bi2Ir2O7 on the Bi site have been synthesized through solid-state method. The X-ray diffraction and the energy dispersive X-ray spectrometry show the formation of impurity-free polycrystals with cubic structure belonging to the space group Fd-3m. The Raman scattering measurement shows redshift and blueshift of active modes. The resistivity is measured by four-probe method. The resistivity measurement shows for x ≤ 1.5, the samples are metals and for x = 2.0, the sample changes to an insulator. The DC magnetization shows the enhancement of antiferromagnetism with doping. The micromagnetic structure of samples is studied by electron paramagnetic resonance. The electron paramagnetic resonance shows generally consistent behavior of major parameters (the absorption peak, g factor, linewidth, normalized intensity) at low temperature. All the parameters show strong dependence on temperature. The results show that the microscopic and macroscopic properties are consistent. [ABSTRACT FROM AUTHOR]

A mononuclear five‐coordinate Cu(II) complex [Cu(12‐TMC)Cl][B(C6H5)4] (1) (12‐TMC = 1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane) with distorted square pyramidal geometry has been synthesized and characterized by single‐crystal X‐ray diffraction, direct‐current and alternating‐current magnetic measurements and electron paramagnetic resonance (EPR) spectroscopy. The complex displays slow magnetic relaxation under an external dc field. The analysis of the field‐ and temperature‐dependence of the relaxation rates suggests that the slow dynamics of the magnetization is dominated by the Raman‐like process in the temperature range of 1.8 K to 11 K under an applied dc field of 0.15 T. In addition, the results of magnetic dynamics for the diluted sample with diamagnetic Zn(II) ions confirms the molecular origin of slow magnetic relaxation. [ABSTRACT FROM AUTHOR]

We report a detailed study of magnetic properties in manganite (LaPr)CaMnO. In contrast to the usual beliefs, it shows an abnormal upturn deviation from the Curie-Weiss law on the inverse susceptibility curve. Such a non-Griffiths-like phase is further confirmed from the inverse double integrated intensities of electron paramagnetic resonance spectrum. Because La $$^{3+}$$ ions are substituted by Pr $$^{3+}$$ ions with 50% concentrations, the ratio of three ions (La $$^{3+}$$ , Pr $$^{3+}$$ , Ca $$^{2+}$$ ) is close to 1 on A-site sublattice. As a result, some short-range antiferromagnetic (CO AFM) phases come into being in the system due to the existence of localized charge ordering states. Therefore, the upturn deviation from Curie-Weiss law originates from the appearance of short-range CO AFM correlations above $$T_{\text{C}}$$ . Additionally, a magnetic field-driven-metamagnetic transition is found, which gives a main contribution for the large magnetic entropy change (MEC) observed in this sample. Both the Arrott plot and the renormalized MEC curves testify that this transition belongs to first-order magnetic transition. The insignificant hysteresis loop indicate that the inevitable thermal hysteresis can be ignored in the present first-order material implying that it is a potential candidate for the cryogenic temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The pyrochlore iridatehas been investigated by means of the electron paramagnetic resonance spectroscopy. A magnetic transition at20 K is found in addition to the transition at130 K, which has not been reported previously. The phase transition at, which corresponds to a resistivity transition, is resulted from the long-range spin ordering ofions in all-in/all-out state. However, the magnetic transition at, which is regardless of resistivity transition, is not caused bybutions. Both of the magnetic transitions are irrelevant to the lattice distortion. We suggest that the competition between the enhanced paramagnetism ofions and thef–dinteraction should be responsible for the magnetic transition at. [ABSTRACT FROM PUBLISHER]

Development of efficient and affordable electrocatalysts in neutral solutions is paramount importance for the renewable energy. Herein, we report that the oxygen evolution reaction (OER) performance of Co3S4 under neutral conditions can be enhanced by exposed octahedral planes and self-adapted spin states in atomically thin nanosheets. A HAADF image clearly confirmed that the active octahedra with Jahn-Teller distortions were exposed exclusively. Most importantly, in the atomically thin nanosheets, the spin states of Co3+ in the octahedral self-adapt from low-spin to high-spin states. As a result, the synergistic effect endow the Co3S4 nanosheets with superior OER performance, with exceptional low onset overpotentials of circa 0.31 V in neutral solutions, which is state-of-the-art among inorganic non-noble metal compounds. [ABSTRACT FROM AUTHOR]

In this paper, we present the investigations of electron paramagnetic resonance on perovskite manganite PrSrMnO and Ga-doped PrSrMnGaO. The temperature dependent paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak linewidth Δ H and double integrated intensities) have been used to study the paramagnetic spin correlations and spin dynamics. The gradual increase of effective g-factor is attributed to the presence of orbital ordering above T. The model fittings of temperature dependent double integrated intensities reveal Arrhenius law is appropriate for describing PrSrMnGaO instead of PrSrMnO system. As for PrSrMnO, the broadening of linewidth with the temperature increase origins from the contribution of small polaron hopping in the PM regime. However, as for PrSrMnGaO, the broadening of EPR linewidth can be understood with the spin-lattice relaxation mechanism. [ABSTRACT FROM AUTHOR]

A spinel sulphide CuIr2S4single crystal, which exhibits an orbitally induced Peierls phase transition at ∼230 K, is investigated by electron spin resonance (ESR) spectroscopy. The phase transition is clearly manifested on the ESR spectra. It is suggested that the ESR signals are produced by a few non-dimerized Ir4+ions. Moreover, an extra ESR spectrum appears at low temperature in addition to the paramagnetic ESR signals of Ir4+ions, which is suggested to be caused by the Jahn–Teller effect of the non-dimerized Ir4+ions. From the ESR results, it is found that the Jahn–Teller splitting energy ΔEJTis much smaller than the spin-dimerization gap. [ABSTRACT FROM AUTHOR]

The effects of As doping on the superconductivity and magnetism in the TlKFeSe superconductor are studied. We find that the As doping does not significantly change the occupancy at the Fe-site, meaning a certain amount of Fe ions changes its valence from 2+ to 3+. The superconductivity is gradually suppressed with increasing As doping. The magnetic measurements suggest that though the As doping does not destroy the antiferromagnetic order in the system, it induces an increase in the staggered magnetic moment. These results suggest that the TlKFeSe system is a system with intrinsic phase separation. The change in the valence state of Fe could be a possible reason for the suppression of superconductivity. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we investigate the polycrystalline , which exhibits an orbitally induced Peierls phase transition at , by the electron spin resonance (ESR) spectroscopy. A corresponding change occurs to the ESR spectra, as well as in the obtained ESR parameters such as resonance field H r and g-factor . It is suggested that the ESR signals originate from the paramagnetic moments caused by lattice defects, which are affected by the spin-dimerization transition. However, ESR signals from a few non-dimerized maybe also exist. In addition, an anomalous change below is detected by the ESR parameters. A possible explanation was proposed to interpret the experimental results. [Copyright &y& Elsevier]

The magnetic states of the BaFe2-xCoxAs2 single crystal samples have been studied by magnetization and electron spin resonance measurements. We find a transformation of the Fe2+ spin state from high temperature high-spin state to low temperature low-spin state, indicating a small crystal field splitting energy. In the superconducting samples, both the magnetization and electron spin resonance results suggest an itinerant behavior of the system. [ABSTRACT FROM AUTHOR]

The transport property of chalcogenide spinel CuCr 2 Se 4 with an itinerant ferromagnetic ground state can be modulated by doping of bromine, where the half-metallic state can be realized around x = 0.25 in CuCr 2 Se 4− x Br x system. In this work, the single crystal CuCr 2 Se 4− x Br x ( x = 0.25) with the cleave surface (111) plane has been investigated by the electron paramagnetic resonance (EPR) spectroscopy. The EPR results show that the in-plane magnetization is strong while the out-of-plane one is weak, which indicate that the spins are ferromagnetic ordered within the (111) plane. In addition, the isothermal EPR spectra in the ferromagnetic phase display that the spin coupling strength ( λ ) and crystal field (Δ CF ) depend on the rotation angle φ as relation λ /Δ CF ∝ cos  φ . Moreover, the peak-to-peak linewidth Δ H PP increases linearly with the decrease of temperature, which suggests that the spin-orbit coupling is enhanced linearly with temperature cooling. [ABSTRACT FROM AUTHOR]

The polycrystals of S = 1/2 spin-dimer compound BaCu(SeO 3) 2 have been synthesized by using solid-state reaction. Without long-range order, the magnetic susceptibility χ (T) curve presents two anomalies at T 1 = 5 K and T G = 58 K due to antiferromagnetic (AFM) short-range order and short-range ferromagnetic (FM) correlations, respectively, which is further supported by the specific heat and electron spin resonance data. The high-temperature χ (T) curve follows the Curie-Weiss law with θ CW = 11.3 K, showing the dominant intradimer FM interaction. The magnetization M (H) curve at 2 K is characteristic of an AFM-FM transition at 0.4 T, suggesting the weak interdimer AFM couplings. The density function theory calculations and quantum Monte Carlo simulations allow an estimation of the intradimer and interdimer exchanges with J 1 / k B = 39.09 K, J 2 / k B = −1.51 K, and J 3 / k B = −1.68 K. Interestingly, the χ −1(T) curve within θ CW < T < T G deviates downward from paramagnetic Curie-Weiss behavior, mimicking the Griffiths-like phase. This is further supported by the ac magnetic susceptibility and magnetic relaxation measurements. The competing intradimer FM and interdimer AFM exchanges with a subtle ratio between them are proposed to be responsible for the formation of Griffiths-like phase. [Display omitted] • Spin-dimer compound BaCu 2 (SeO 3) 2 has been successfully synthesized. • The χ −1(T) curve within θ CW < T < T G deviates downward from PM Curie-Weiss behavior, mimicking the Griffiths-like phase. • The DFT calculations show that the intradimer interaction is FM with J 1 / k B = 39.09 K, the interdimer couplings are weak. • The magnetization reaches 1.06 μ B /Cu2+ at 30 T, very close to the saturated value of 1.08 μ B /Cu2+ (g = 2.15 from ESR). [ABSTRACT FROM AUTHOR]

A chiral soliton lattice (CSL) is a topological spin-texture that has potential applications in next-generation spintronic devices. In this work, we performed angle-dependence of magnetization and electron spin resonance (ESR) investigations on the CSL host Yb(Ni1−xCux)3Al9 with x = 0.06 (YNCA). The angle-dependent magnetization reveals a peculiar variable magnetic anisotropy. The maximum magnetization axis is parallel to the ab-plane below the field of ∼35.7 kOe while shifts to the c-axis at higher fields. The microwave responses of the CSL helicoid and ferromagnetic resonance (FMR) of the forced ferromagnetic state (FFM) are observed and appear as two resonance lines on ESR spectra with the highest intensities in the ab-plane. When the external field is rotated from H ⊥ c to H / / c , the resonance field H r 1 corresponding to the CSL helicoid decreases while H r 2 correlated with the FMR increases. Furthermore, the temperature-dependent ESR shows that the CSL persists until 15 K much higher than TC (6.4 K), which suggests a precursor phenomenon. The microwave response in YNCA provides a powerful tool for modulating and researching the CSL. [ABSTRACT FROM AUTHOR]

The electric and magnetic properties of doped iridates Y 2 Ir 2- x Cu x O 7 have been studied in the present paper. It is found that the magnetic properties show an enhanced ferromagnetism with doping, which comes from Cu spins and doping-broken Ir networks. The M–T data of all the doped compounds show a magnetic order around 150 K, which should be rooted in antiferromagnetic (AFM) order of Ir spins. However, there is also another transition below 20 K for x ≥ 0.2 samples, which should be originated from AFM Cu-Ir interactions. The result of bulk magnetization can be further proved by Electron spin resonance (ESR) measurements which suggest ferromagnetic (FM) interactions of Cu ions and the occurrence of magnetic order below 20 K. From the data of M – H curves, we found that there is a metamagnetic-like transition at 20 kOe for all the doped samples, which is considered as reconstruction of the Ir electrons. While another metamagnetic-like transition at 60 kOe for x = 0.4 sample is observed and considered as a spin-reorientation Cu spins. Resistivity data indicate that all the doped samples can be fitted by Mott's variable-range hopping (VRH) model at low temperatures. This is the consequence of localization due to disorder on the Ir/Cu site. • Magnetic properties show an enhanced ferromagnetism with doping. • There is another transition below 20 K with doping due to AFM Cu-Ir interactions. • The two metamagnetic-like transitions are due to a spin-reorientation of Ir and Cu. • The conduction of the doped samples is explained with VRH mechanism due to disorder. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) was applied extensively to probe the phase separation and spin relaxation mechanism in the perovskite manganites. In this study, we conducted the measurement of EPR for the perovskite manganites (La 0.5 Pr 0.5 ) 0.67 Ca 0.33 MnO 3 . We found that both paramagnetic and ferromagnetic resonance peaks simultaneously emerged on resonance spectrum near below T C , exhibiting a typical characteristic of phase separation. The linewidth of EPR spectrum progressively enlarged upon the rising of temperature in the temperature range of T > T C and a quasilinear variation of peak-peak width was observed at T C < T < 500 K. In contrast to the usual beliefs that the variation of peak-peak linewidth can be understood either by spin-lattice relaxation or by spin-spin relaxation, however, the linewidth behavior observed here shows a coexistence of two spin relaxation mechanisms. We proposed that the inhomogeneous electronic phases due to the intrinsic self-organizing growth were responsible for the appearance of multiple spin exchange interactions and variational relaxation mechanism. This finding would be possible to pave a new way for further investigating magnetic correlations and spin dynamics in the paramagnetic hole-doped manganites. [ABSTRACT FROM AUTHOR]

Abstract: We report the magnetic, specific heat and electron spin resonance (ESR) studies on Ba3MnNb2O9, as one of quasi-two-dimensional triangular–lattice magnet. The magnetic susceptibility and specific heat measurement show that it undergoes an magnetic transition at T N =3.2K. The magnetic capacity (C mag ) follows T 2 dependence, and magnetic entropy (S mag ) reaching to 14.5JK−1mol−1 at 32K satisfactorily agrees with the theoretical estimations of Mn2+ ion in high-spin configuration with S=5/2. From the ESR spectra, the Landé factor (g eff ), the linewidth (ΔH pp ) and the ESR intensity (I) are derived and analyzed as a function of temperature. As temperature decreases to T ⁎~18K, the g-factor shows a minima with g eff =1.984(2) before shifts to larger value at lower temperatures, and the ESR intensity starts to be suppressed below this temperature. This anomalous phenomenon is explained in terms of the establishment of short-range AFM spin correlations at much higher temperatures above T N . [Copyright &y& Elsevier]

[Display omitted] • Fe 2.71 Se 4 (dien) 2 was obtained by assembly of FeSe 2 chains and Fe(dien) 2 complexes. • High Fe vacancies induce the long-range ferrimagnetic order in Fe 2.71 Se 4 (dien) 2. • Magnetic properties are tuned by varying x from 0.86 to 1.23 in Fe 2x+1 Se 4 (dien) 2. Challenges still remain in producing room-temperature ferromagnetism/ferrimagnetism in inorganic–organic hybrid compounds. Here, we report the Fe vacancy-doped inorganic–organic (Fe x Se 2) 2 Fe(dien) 2 (dien = diethylenetriamine, x = 0.86) hybrid cuboids by self-assemble of finite one-dimensional (1D) FeSe 2 chains and Fe(dien) 2 complexes. A growth model is proposed by kinetically controllable syntheses of novel Fe 2x+1 Se 4 (dien) 2 hybrids. The Rietveld refinement reveals that Fe vacancies in the Fe 2.71 Se 4 (dien) 2 hybrid cuboids induce large distortions of the FeSe 2 chains and the room-temperature lattice parameters are a = 9.225(4) Å, b = 18.021(8) Å and c = 11.609(6) Å. Magnetic measurements and electron spin resonance spectra of the Fe 2.71 Se 4 (dien) 2 hybrid cuboids show the ferrimagnetism with the Curie temperature (T C) of 600 K and the spin glass state with the freezing temperature (T f) of 108 K. Impressive room-temperature ferrimagnetic properties of the Fe 2.71 Se 4 (dien) 2 hybrid cuboids were ascribed to the high concentration of Fe3+ vacancies (0.29 per cell) in the hybrid cuboids, which is supported by the 57Fe Mössbauer spectrum fitting based on the ferrimagnetic model. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic entropy around the paramagnetic–ferromagnetic (PM–FM) phase transition temperature has been investigated for chromium based spinel CdCr2Se4. It is found that magnetic entropy changes are generated by the spin–lattice coupling, which can be easily modulated by the external magnetic field. The electron paramagnetic resonance (EPR) study proves the existence of the spin–lattice coupling above , and reveals the stronger coupling at . In addition, the variation of the micro-structure due to the spin–lattice interaction has been observed around from the measurement of the low-temperature X-ray diffraction. [ABSTRACT FROM AUTHOR]