High-field Magnetization Process Research Articles

Synthesis and magnetic properties of tetragonally ordered Fe2Ni2N alloy using topotactic nitriding reaction

Tetragonally ordered Fe2Ni2N powder was successfully synthesized from L10-FeNi using a nitrogen topotactic reaction. The magnetic properties and structural stability of the tetragonally ordered Fe2Ni2N were examined using first principles calculations. The nitriding process gives 96 wt% of tetragonally ordered Fe2Ni2N phase and the rest is the more nitrided phase of FeNiN. Analysis of the crystal structure confirmed that the c/a is 0.989 for the tetragonally ordered Fe2Ni2N, which is consistent with the results of the first-principles calculations. Magnetization measurements reveal that the Curie temperature and thermal decomposition temperatures are 441 and 667 K, respectively. The high field magnetization processes at 10 K indicate that the sample contains a component of high magnetic anisotropy energy Ku. The Ku estimated by the law of approach to ferromagnetic saturation is 1.51 MJ/m3, which is in reasonably good agreement with that obtained by the first-principles calculations 1.96 MJ/m3.

Magnetization plateau observed by ultrahigh-field Faraday rotation in the kagome antiferromagnet herbertsmithite

To capture the high-field magnetization process of herbertsmithite (ZnCu3(OH)6Cl2), Faraday rotation (FR) measurements were carried out on a single crystal in magnetic fields of up to 190 T. The magnetization data evaluated from the FR angle exhibited a saturation behavior above 150 T at low temperatures, which was attributed to the 1/3 magnetization plateau. The overall behavior of the magnetization process was reproduced by theoretical models based on the nearest-neighbor Heisenberg model. This suggests that herbertsmithite is a proximate kagome antiferromagnet hosting an ideal quantum spin liquid in the ground state. A distinguishing feature is the superlinear magnetization increase, which is in contrast to the Brillouin function-type increase observed by conventional magnetization measurements and indicates a reduced contribution from free spins located at the Zn sites to the FR signal.

The Structural Relaxation and its Influence on High Field Magnetization Processes

Abstract In this paper the results of the structural and magnetic investigation of Fe61Co10Y8Zr1B20 alloy after solidification and isothermal annealing was presented. The isothermical annealing was carried out at 700 K for 1 h and 770 K for 3.5 h. For the structural investigation was performed by X-ray diffractometer equipped with a copper lamp. The results of (XRD) measurements showed the material in the state after the solidification and heat treatment is amorphous. Static hysteresis loops and initial magnetization curve was measured using vibrating magnetometer (VSM). The quality and quantity of structural defects in the sample after heat treatment was determined by indirect method using analyze the initial magnetization curve in accordance with the theory of Kronmüllera. These studies have shown that the annealing process has big influence to change significantly quantity of defects in amorphous structure as a result, there are changes of magnetic parameters such as saturation magnetization and field μ0Ms coercivity Hc.

High-field multi-frequency ESR in the S=2 heisenberg antiferromagnetic chain compound MnCl3(bpy)

We report the results of high-field multi-frequency electron spin resonance (ESR) experiments on a powder sample of MnCl3 (bpy) (bpy=2, 2′-bipyridine). This compound is one of the rare examples of the spin (S) 2 quasi one-dimensional (1D) Heisenberg antiferromagnets (HAFs), and magnetic properties of tiny single crystal samples were reported previously (G. E. Granroth et al., Phys. Rev. Lett. 77, 1616 (1996).). In our previous paper on this compound (M. Hagiwara et al., J. Phys.: Conf. Ser. 400, 032014 (2012).), we reported, for the S=2 1D HAF, good agreement between experiment and calculation for the temperature dependence of magnetic susceptibility and the high-field magnetization process at 1.3 K. In this work, we have observed some high-frequency resonance modes with zero-field gaps of about 800 GHz that may correspond to antiferromagnetic resonance modes with orthorhombic anisotropy in a long-range-ordered phase that emerged at low temperatures above the critical field at which the energy gap (Haldane gap) closes. The single-ion anisotropy constant D evaluated from the analysis of these ESR modes is larger than that reported previously.

Antiferromagnetic ordering in Sr2CrO4

The magnetic ground state of Sr2CrO4 with a distorted honeycomb lattice was investigated by means of measurements of the magnetic susceptibility, high-field magnetization process, and electron spin resonance (ESR). Antiferromagnetic ordering was observed clearly below TN = 3.2 K, while the magnetic ground state had been thought to be a spin-singlet state. A two-sublattice model with biaxial anisotropy was applicable for the observed ESR modes. Plateau-like behavior and a sharp kink were detected in the magnetization curve.

High-Field Magnetization Study of $R_{2}{\rm Fe}_{17}{\rm H}_{3}$ ($R={\rm Tb}$, Dy, Ho and Er) Single-Crystalline Hydrides

The high-field magnetization process in the hydrogen-charged R2Fe17H3 (R=Tb , Dy, Ho and Er) single crystals is studied along principal crystallographic directions at T=4.2 K and compared with that of the known parent R2Fe17 compounds. Substantial changes of the magnetic anisotropy behavior induced by hydrogenation are found. Depending on the rare earth atom, the R2Fe17H3 compounds possess the “easy-axes”, “easy-cone” and “easy-plane” types of magnetocrystalline anisotropy (MCA), whereas the precursors R2Fe17 have the easy-plane type of MCA only. The various observed types of the field-induced phase transitions in R2Fe17H3 are discussed and information on the effect of hydrogen on the strength of R-Fe coupling is obtained.

Mapping the magnetic phase diagram of the frustrated metamagnetCuFeO2

The magnetic phase diagram of ${\text{CuFeO}}_{2}$ as a function of applied magnetic field and temperature is thoroughly explored and expanded, both for magnetic fields applied parallel and perpendicular to the material's $c$ axis. Pulsed field magnetization measurements extend the typical magnetic staircase of ${\text{CuFeO}}_{2}$ at various temperatures, demonstrating the persistence of the recently discovered high-field metamagnetic transition up to ${T}_{N2}\ensuremath{\approx}11\text{ }\text{K}$ in both field configurations. An extension of the previously introduced phenomenological spin model used to describe the high-field magnetization process [T. T. A. Lummen, C. Strohm, H. Rakoto, A. A. Nugroho, and P. H. M. van Loosdrecht, Phys. Rev. B 80, 012406 (2009)] is applied to each of the consecutive low-field commensurate spin structures, yielding a semiquantitative simulation and intuitive description of the entire experimental magnetization process in both relevant field directions with a single set of parameters.

High-Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa2S4

We report the experimental and the analytical results of electron spin resonance (ESR) and magnetization in high magnetic fields up to about 68 T of the quasi two-dimensional triangular lattice antiferromagnet NiGa$_2$S$_4$. From the temperature evolution of the ESR absorption linewidth, we find a distinct disturbing of the development of the spin correlation by $Z_2$-vortices between 23 K and 8.5 K. Below $T_{\rm{v}}=8.5$ K, spin-wave calculations based on a 57$^{\circ}$ spiral spin order well explains the frequency dependence of the ESR resonance fields and high field magnetization processes for $H$$\parallel$$c$ and $H$$\perp$$c$, although the magnetization for $H$$\perp$$c$ at high fields is different from the calculated one. Furthermore, we explain the field independent specific heat with $T^2$-dependence by the same spin-wave calculation, but the magnitude of the specific heat is much less than the observed one. Accordingly, these results suggest the occurrence of a $Z_2$ vortex-induced topological transition at $T_{\rm{v}}$ and may indicate quantum effects beyond the descriptions based on the above classical spin models.

High-Field Magnetization Measurements for a Single Crystal of Er2Fe17H3 Hydride

High-field magnetization process of the single crystal of Er2Fe17H3 is investigated and compared with that of the parent Er2Fe17 in order to clarify the effect of interstitial hydrogen on magnetic properties. Substantial change in the magnetic anisotropy behavior observed for Er2Fe17H3 is explained by the modification of the interaction between the 4f-shell orbital moment of Er and the crystal field leading to the change of the second-order crystal electric field coefficient \(A^{0}_{2}\) . Hydrogenation does not practically affect the intersublattice molecular field.

Magnetic order and interaction in garnet lattice antiferromagnets AgCa2M2V3O12(M=Mn, Co, Ni) and NaPb2Mn2V3O12

We have investigated the magnetic orderings and the magnetic interactions in garnet antiferromagnets AgCa2M2V3O12(M=Mn, Co, Ni) and NaPb2Mn2V3O12, using the powder neutron diffraction and magnetization measurements. In the neutron diffraction measurements, we revealed that the magnetic structures in all samples measured are simple two sublattice antiferromagnetic structures with collinear magnetic moments. We also determined the exchange interactions from the critical magnetic fields Hsat observed in the high field magnetization processes up to 30 T.

High-field magnetization process of O2 adsorbed in a microporous coordination polymer CPL-1 at various temperatures

High-field magnetization measurements have been performed at various temperatures on the molecular oxygen adsorbed in a microporous coordination polymer CPL-1. Molecular oxygen with S = 1 forms O2-O2 dimer in the nanochannels of CPL-1. The magnetic properties can be explained by not the S = 1 Heisenberg antiferromagnetic dimer model but the O2-O2 dimer model taking into account the spin-dependent intermolecular potential. This feature is attributed to the fact that the magnetic interaction between O2 is comparable to the van der Waals force.

High field magnetization processes in single crystals of α-Tb2S3 and α-Dy2S3

Rare earth sesquisulfides α-Tb2S3 and α-Dy2S3 possess orthorhombic crystal structure having two independent rare earth sites. High field magnetization processes for single crystals of these compounds have been investigated up to μoH = 18 T. Some step-like transitions have been observed in both compounds. The magnetization of α-Tb2S3 single crystal under the field along the 6-axis at T = 1.4 K shows a steep increase of about 4.5 μB, which corresponds to a half of full saturation moment of free Tb3+, at μoH = 2.2 T. It is considered that the reorientation of Tb3+ moments on only one Tb site into a ferromagnetic arrangement occurs. When the magnetic field is perpendicular to the b-axis, one-step transition at μoH = 0.7 T for H∥c and two-step transitions at 0.7 and 1.2 T for H∥a are observed. As for α-Dy2S3, the magnetization curve at T = 1.5 K shows two-step transitions at 1.3 and 1.6 T (H∥b), three or four dull steps (H∥a or c). The total height of two steps in the M-H curve for H∥b corresponds to a half of full Dy3+ moment.

Instability of the Co magnetic state in Y 2Co 7-based compounds: Effect of alloying for Y- and Co-sites

High field magnetization process has been studied in the (Y 1− x Zr x ) 2Co 7, (Y 1− x U x ) 2Co 7 and Y 2(Co 1− x Al x ) 7 systems in order to reveal the possibility of the transformation of the Co magnetic ions from the high to the low moment state. The spontaneous magnetic moment, Curie temperature and anisotropy constant have been found to decrease monotonously with increasing x in the single phase interval. The results suggest that the Co moment in present systems is unstable with respect to both electron concentration and exchange interactions. The average Co moment reduces to the value characteristic of the YCo 3 compound. However, no signatures of the formation of the low moment Co state was found in the studied Y 2Co 7-based systems.

1/3 Magnetization Anomaly in Triangular Spin Prism

A high-field magnetization process for the triangular spin prism Na 17 [Mn 6 (H 2 O) 2 (AsW 9 O 34 ) 2 (AsW 6 O 26 )]·38H 2 O, which consists of six Mn 2+ ions ( S =5/2), has been investigated. The magnetization at low temperature shows a 1/3 plateau around 5.5 T. It is examined by theoretical calculations using exact diagonalization. The experimental results can be reproduced, but only in a restricted parameter range. It implies that the plateau originates from a delicate balance of exchange couplings. We propose that the plateau is stabilized by some external perturbations, such as thermal/quantum fluctuations.

Field-induced transitions in single crystals of TbCu4Ag and GdCu4Ag

Measurements of magnetization were carried out for single crystals of TbCu4Ag and GdCu4Ag under magnetic field up to 18 T at temperatures of 1.7, 3.0 and 4.2 K. At 4.2 K, two stepped field-induced transitions were observed in magnetizing process along all the [111], [110] and [100] directions. At 1.7 K four stepped transitions were observed only along the [100] direction. For GdCu4Ag unusual increase of magnetization was observed in high field magnetization process.

Ferro-Antiferromagnetic Delta-Chain System Studied by High Field Magnetization Measurements

High field magnetization processes were measured for the single crystal of an S = 1/2 ferro-antiferromagnetic delta-chain system [Cu(bpy)(H 2 O)][Cu(bpy)(mal)–(H 2 O)](ClO 4 ) 2 . At low temperatures, the observed magnetization curve shows a rapid increase to half of the saturation moment below about 1 T and then followed by a gradual increase to fully polarized state below about 7 T. Concerning this characteristic magnetization process, we discuss the ground state of the system qualitatively based on a non-interacting two sublattice model, where a delta-chain is divided into apical free spins and remaining basal spins regarded as quasi one dimensional antiferromagnetic chain. Essential effect of ferromagnetic interaction, which connects an apical spin and basal spins, is pointed out from the comparison with theoretical curve for the non-interacting two sublattice model as well as with the numerically calculated curve. Presence of the Dzyaloshinskii–Moriya interaction is also suggested from the arguments ...

High-field magnetization process in novel TbFeCo/YFeCo magnetostrictive spring magnet type multilayers

Magnetization process of conventional and discontinuous magnetostrictive spring magnet type multilayers (CMSMM and DMSMM, respectively) is investigated by means of magnetization, magnetostriction and magnetic force microscopy for sputtered Tb 0.4(Fe 0.55Co 0.45) 0.6/Y x Fe 1− x and Tb 0.4(Fe 0.55Co 0.45) 0.6/Y x (Fe 0.7Co 0.3) 1− x (denoted as Terfecohan/Y x Fe 1− x and Terfecohan/Y x (Fe,Co) 1− x , respectively) multilayers with a variable Y-content 0 ≤ x ≤ 0.2. Various magnetic behaviour such as in-plane magnetic anisotropy, out-of-plane magnetic anisotropy, field-induced transition and exchange bias phenomenon are observed. Optimization of large magnetostriction and large magnetostrictive susceptibility are discussed in terms of the magnetization reversal, exchange coupling between sandwiched amorphous TbFeCo and nanostructured YFeCo-layers.

Magnetic Properties of Molecular Oxygen Adsorbed in Micro-Porous Metal-Organic Solids

The magnetic properties of O2 adsorbed in nanochannels of porous metal-organic solids CPL-1 and CPL-p1 have been investigated by means of high-field magnetization process measurement. The contribution from adsorbed O2 shows the metamagnetic-like behavior in both compounds. We propose “the field-induced rearrangement mechanism” as the explanation for the metamagnetic-like behavior. It is known for the O2-O2 dimer that the magnetic interaction depends strongly on the intermolecular distance and the orientation of molecular axes. It is considered naturally that the stable arrangement with saturated magnetic moment in the sufficient high field is different from the H-structure which is stable at zero field.

Magnetism of a one-dimensional array of oxygen in a micro-porous metal-organic solid

Abstract The magnetic properties of molecular oxygen adsorbed in the micro-porous metal-organic solids have been investigated. Adsorbed O 2 molecules form a ladder structure in the nanochannels of CPL-1. The temperature dependence of susceptibility and the high-field magnetization process indicate the nonmagnetic ground state of the adsorbed O 2 at low temperatures.

High field magnetization processes of BIPNNBNO and PIMBNO at low temperature

Abstract The magnetizations of organic spin systems BIPNNBNO and PIMBNO were measured at 400 mK in high magnetic fields up to 40 T . BIPNNBNO has a spin gap, which is closed at 4.5 T . Magnetization plateaux of 1 3 and 2 3 are found at 7– 22 T and around 25 T , respectively. Above 28 T , the magnetization is completely saturated. The magnetization of PIMBNO increases super-linearly with field and saturates to 1μB/f.u. above 8 T .