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Motivated by the multiferroic effects and quantum magnetization plateaus in the skew chain antiferromagnets T 2 V 2 O 7 (T = Ni, Co), we have conducted a detailed density function theoretical study on Co 2 V 2 O 7. The results show that the nearest-neighbor interchain interaction (J 3 / k B = − 35.57 K) is not much greater than the intrachain interactions (J 1 / k B = − 19.54 K and J 2 / k B = 27.55 K), showing the absence of interchain dimerization of the Co ions. This indicates that the "dimer+monomer" model used for Ni 2 V 2 O 7 [Cao et al., Phys. Rev. B 106, 184409 (2022)] is no longer applicable to Co 2 V 2 O 7. Finally, the exact diagonalization of spin Hamiltonian, including anisotropic exchanges, produces the experimentally observed 1/2 and 3/4 magnetization plateaus. [ABSTRACT FROM AUTHOR]

Motivated by the multiferroic effects and quantum magnetization plateaus in the skew chain antiferromagnets T 2 V 2 O 7 (T = Ni, Co), we have conducted a detailed density function theoretical study on Co 2 V 2 O 7. The results show that the nearest-neighbor interchain interaction (J 3 / k B = − 35.57 K) is not much greater than the intrachain interactions (J 1 / k B = − 19.54 K and J 2 / k B = 27.55 K), showing the absence of interchain dimerization of the Co ions. This indicates that the "dimer+monomer" model used for Ni 2 V 2 O 7 [Cao et al., Phys. Rev. B 106, 184409 (2022)] is no longer applicable to Co 2 V 2 O 7. Finally, the exact diagonalization of spin Hamiltonian, including anisotropic exchanges, produces the experimentally observed 1/2 and 3/4 magnetization plateaus. [ABSTRACT FROM AUTHOR]

We report the decoupling of Gd–Cr magnetism and the resulting giant magnetocaloric effect in honeycomb-lattice tellurate GdCrTeO6. This compound adopts the hexagonal structure with the space group P-3. The susceptibility curve presents a paramagnetic behavior from room temperature to 2 K. Very intriguingly, however, the heat capacity measurement probes a λ-like peak at TN = 10 K, characterizing the long-range antiferromagnetic order. This suggests that the Gd and Cr sublattices are magnetically independent, i.e., the Gd ions are paramagnetic and the strong paramagnetism nearly masks the antiferromagnetic order of Cr ions, which is further evidenced by our ESR data. The maximum magnetic entropy change at 2 K is 41.8 J kg−1 K−1 in a field range of 0–7 T and 30.3 J kg−1 K−1 for 0–3 T, larger than those of most of the Gd oxides reported. The observed giant magnetocaloric effect is due to strong paramagnetism of Gd ions. [ABSTRACT FROM AUTHOR]

The nature of 4f-3d magnetic interaction in oxides as well as its influence on the magnetocaloric effect (MCE) is an interesting topic. Here, we report the weak magnetic interaction and large MCE in a new triangular lattice GdFeTeO6 synthesized by the solid state reaction method. The weak exchange, which was seldom observed in 4f-3d oxides, is supported by the low ordering temperature (TC ≤ 3 K) and a positive but small Curie-Weiss temperature (θp = 3 K). Under an external magnetic field, the magnetization process yields a large magnetic entropy change of 38.5 J kg−1 K−1 at 5 K for 0-7 T and 23.6 J kg−1 K−1 at 3 K for 0-3 T. Finally, our first-principles calculations demonstrate a ferrimagnetic spin model with the Gd(↑)-Gd(↑)-Fe(↓)-Fe(↓) configuration. The weak magnetic interaction is an average effect of ferromagnetic (4f-4f and 3d-3d) and antiferromagnetic (4f-3d) interactions. The antiferromagnetic 4f-3d interaction is a reason for the reduction of MCE. [ABSTRACT FROM AUTHOR]

The nature of 4f-3d magnetic interaction in oxides as well as its influence on the magnetocaloric effect (MCE) is an interesting topic. Here, we report the weak magnetic interaction and large MCE in a new triangular lattice GdFeTeO6 synthesized by the solid state reaction method. The weak exchange, which was seldom observed in 4f-3d oxides, is supported by the low ordering temperature (TC ≤ 3 K) and a positive but small Curie-Weiss temperature (θp = 3 K). Under an external magnetic field, the magnetization process yields a large magnetic entropy change of 38.5 J kg−1 K−1 at 5 K for 0-7 T and 23.6 J kg−1 K−1 at 3 K for 0-3 T. Finally, our first-principles calculations demonstrate a ferrimagnetic spin model with the Gd(↑)-Gd(↑)-Fe(↓)-Fe(↓) configuration. The weak magnetic interaction is an average effect of ferromagnetic (4f-4f and 3d-3d) and antiferromagnetic (4f-3d) interactions. The antiferromagnetic 4f-3d interaction is a reason for the reduction of MCE. [ABSTRACT FROM AUTHOR]

High-field electron spin resonance (ESR) has been employed to study the antiferromagnetic (AFM) ordering state (T

We have illustrated the presence of spin-glass-like freezing in the Mn-doped spin-chain compounds Ca3Co2-xMnxO6, which was not reported previously. With increasing Mn composition, the magnetic relaxation due to spin freezing is gradually suppressed. Interestingly, the magnetization in the intermediate Mn compositions relaxes more slowly (characteristic time is significantly enhanced) than those in x = 0.0 and 1.0. This could be understood within the framework of disorder with randomness or imperfections, which plays an important role in the formation of spin-glass-like feature in intermediate Mn compositions, quite different from the cases in x = 0.0 with strong spin frustration and in x ∼ 1.0 with perfect Co/Mn ionic order. [ABSTRACT FROM AUTHOR]

We investigated the structure and magnetic properties of the multiferroic hexagonal manganite Y1-xTbxMnO3 (x = 0, 0.1, 0.2) single crystals. At 23 K, a Mn spin reorientation transition, which is not reported in the parent compound YMnO3, is observed in Y0.8Tb0.2MnO3. At a lower temperature, another new transition is observed in the doping system, which is attributed to the formation of long range antiferromagntic order of the doped Tb3+ moments. Based on the experimental results, we suggest that the effect of Tb doping is to bring about the increase of the Mn-O-Mn bond angle and the relief of the magnetic frustration. With increasing the doping level, for x = 0.2, when a magnetic field is applied parallel to the c axis, the field induced spin-flop transition is appeared, which indicates the reorientation of the Mn3+ moments along with the field-induced ferromagnetic ordering of the Tb3+ moments. These results suggest that the possibility of the Tb doping can change the magnetic structure and ferroelectricity properties of YMnO3. [ABSTRACT FROM AUTHOR]

We have demonstrated that in Ca3Co2-xScxO6, substitution of nonmagnetic Sc3+ (S = 0) for high-spin Cotrig, even up to the solid solubility limit of x = 0.5-0.6, does not dramatically modify the intrachain ferromagnetic (FM) interaction. This is quite different from the cases of Ir- and Rh-doping, which much enhance the intrachain FM interaction, and the cases of Mn-, Fe-, and Cr-doping, which gradually reduce the intrachain FM interaction, simultaneously introducing antiferromagnetic interaction. The results of band-structure calculations of x = 0.5 are qualitatively consistent with our magnetization data. [ABSTRACT FROM AUTHOR]

Various types of anomalies of inverse dc susceptibility (H/M) have been observed in spin-chain compounds Ca3Co2-xMnxO6. For x = 1.0, the H/M curve exhibits a field-dependent downturn from the paramagnetic Curie-Weiss behavior, signaling the presence of a Griffiths-like cluster phase. A slight decrease of x leads to a rapid suppression of the Griffiths-like singularity, followed by an appearance of field-independent, non-Griffiths-like behavior at x = 0.92. This feature persists until x = 0.33, at and below which the H/M curve presents an unambiguous, field-independent upturn from the Curie-Weiss law. These Mn-doping-dependent anomalies of H/M curves are associated with complex competing magnetic interactions. [ABSTRACT FROM AUTHOR]

Measurements of isothermal magnetization and electrical transport on Pr0.5Ca0.5Mn0.97Ga0.03O3 have been performed in a magnetic field up to 15 T. Two distinct metamagnetic transitions, which may relate to the collapse of the pseudo-CE-type and CE-type antiferromagnetic phases (CE, a composite antiferromagnetic structure composed of a chequeboard of alternating C and E type), have been observed in the temperature region of 2.5-140 K. Different from the traditional magnetization steps, the two metamagnetic transitions are not dependent on the field sweep rate. These peculiar features are sensitive to the microstructure of the sample. A temperature-field phase diagram has been constructed and found to exhibit a minimum critical field, similar to other phase-separated systems. [ABSTRACT FROM AUTHOR]

We have performed magnetization measurements of Gd5Ge4 with little or no ferromagnetic (FM) impurities under a pulsed magnetic field up to 40 T. The results reveal previously undetected transitions between 85 and 105 K, that is, a distinct second-order antiferromagnetic (AFM)-paramagnetic (PM) transition, followed by a first-order PM-ferromagnetic (FM) transition. The distinct variation of the slope of the M(H) curves is observed around the AFM-PM transition. Combining our high-field data and those reported earlier, a new magnetic field-temperature phase diagram, in which the AFM, PM, and FM states are well separated, is constructed. [ABSTRACT FROM AUTHOR]

Unusual magnetization process has been observed in Gd5Ge4 prepared with commercial Gd of 99.9 wt %. First, the zero-field-cooled M(H) curves below 25 K contain a significant low-field ferromagnetic (FM) component followed by an unusually broadened field-induced antiferromagnetic (AFM)-FM transition, which was not observed in previous reports no matter if the sample owns a residual FM component or not. Second, the M(H) curves at 4.2 K collected using pulsed magnetic fields reveal some unusual dynamics on the low-field FM state and the following AFM-FM transition. Thus, the present sample of Gd5Ge4 is a new example showing complexity of the influence from impurities of Gd upon the magnetization process. [ABSTRACT FROM AUTHOR]

The unusual low field magnetic behavior is revealed in the dc and ac magnetic susceptibility measurements of Gd5(SixGe1-x)4 (x<∼0.5). These anomalies can be ascribed to the presence of short range ferromagnetic correlations and ferromagnetic clustering in both antiferromagnetic and paramagnetic states. As a result, a novel triangular regime is discovered in the low field magnetic and crystallographic temperature-composition (T-x) phase diagram. The nature of paramagnetic state in this regime can be understood within the framework of Griffiths-like model, which not only originates from the disorder and the modification of competing interslab and intraslab magnetic exchange interactions induced by orthorhombic-monoclinic structural distortion but also correlates with the thermal history or initial magnetic disordering. [ABSTRACT FROM AUTHOR]

The unusual low field magnetic behavior is revealed in the dc and ac magnetic susceptibility measurements of Gd5(SixGe1-x)4 (x<∼0.5). These anomalies can be ascribed to the presence of short range ferromagnetic correlations and ferromagnetic clustering in both antiferromagnetic and paramagnetic states. As a result, a novel triangular regime is discovered in the low field magnetic and crystallographic temperature-composition (T-x) phase diagram. The nature of paramagnetic state in this regime can be understood within the framework of Griffiths-like model, which not only originates from the disorder and the modification of competing interslab and intraslab magnetic exchange interactions induced by orthorhombic-monoclinic structural distortion but also correlates with the thermal history or initial magnetic disordering. [ABSTRACT FROM AUTHOR]

X-ray diffraction experiments in pulsed magnetic fields were performed to study the giant magnetic-field-induced strain in the martensitic phase of ordered Fe3Pt alloy. The field dependence of the arrangement of the variants (crystallographic domains) was observed directly in pulsed magnetic fields for the first time. The variants with the c axis perpendicular to the magnetic field are transformed into variants with the c axis nearly parallel to the magnetic field. Moreover, we found that the reorientation behaviors are different for different variants with the same crystallographic direction. The results demonstrate the crucial importance of microscopic investigation, such as x-ray diffraction analysis, of the martensitic transition. We also found that the magnetic-field-induced strain associated with the rearrangement of the variants occurs even in a very fast sweeping pulsed field of up to 1.9×103 T/s at 1 T. [ABSTRACT FROM AUTHOR]

Single-phase Gd[sub 2]Co[sub 17-x]V[sub x] compounds (x = 0.0-1.5) crystallizing in the rhombohedral Th[sub 2]Zn[sub 17] structure have been synthesized. The lattice parameters a and c of the compounds increase linearly with increasing V content, and the rate of increase of c is about 2.5 times as large as that of a. Substitution of a small amount of V atoms (x = 0.3) for Co atoms leads to the occurrence of uniaxial magnetocrystalline anisotropy of Gd[sub 2]Co[sub 17-x]V[sub x]. The anisotropy field H[sub A] increases drastically with increasing V content. The variations of both the lattice parameters and the magnetocrystalline anisotropy with V content suggest a preferential occupation of the V atoms at the 6c dumbbell site. The Curie temperature T[sub C], saturation moment M[sub S], and average Co moment 〈μ[sub Co]〉 of the compounds decrease greatly as the V content increases. The rapid decrease of T[sub C] is essentially attributed to a serious weakening of the Co-Co interactions due to the preferential occupation of the V atoms at the 6c site. The effect of a strong hybridization between the V and Co atoms is plausibly responsible for the decreases of the Ms and 〈μ[sub Co]〉. [ABSTRACT FROM AUTHOR]