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The intermetallic compound Fe 1 − x Co x Si has a helical magnetic order for 0.05 < x < 0.8 , whereas its orbital angular momentum contributing to the occurrence of a Dzyaloshinskii–Moriya interaction has not yet been verified. We applied soft x-ray magnetic circular dichroism spectroscopy on the Fe L 2 , 3 and Co L 2 , 3 edges below T c for Fe 0.75 Co 0.25 Si such that their orbital magnetic moments m orb were evaluated independently. The dichroic signals provide direct experimental evidence that m orb for both Fe and Co is coupled in a parallel manner with each spin counterpart m spin . The ratio of m orb to m spin is independently estimated as m orb / m spin ∼ 3 % for Fe and 9% for Co. By comparing the average of the two m spin values with the saturated magnetization using a commercial superconducting quantum interference device (SQUID) magnetometer, the hole number in the d bands for both Fe and Co is roughly estimated as approximately 1.5. This suggests that Fe and Co should be arranged closely for stabilizing the ferromagnetic moments. [ABSTRACT FROM AUTHOR]

The single crystal of a chiral magnet Cr1/3NbS2 exhibits discrete changes in magnetization (M) in response to changes in magnetic field (H) triggered by the formation of a chiral soliton lattice (CSL). In order to provide evidence of this phenomenon, the study of the size effect is indispensable. We investigated the effects of size on this phenomenon by the use of two single crystals, (A) and (B), whose crystal sizes along the c-axis were 110 µm and 60 µm, respectively. First, in (A), the large jumps of M observed in the process of decreasing H exhibited inconsistent features, whereas the largest and second-largest jumps in (B) exhibited reproducibility for both the value of H and the magnitude of the M jumps. This confirms that these large jumps do not originate from the Barkhausen effect, as this effect would result in M jumps appearing at random values of H. When the system size of a sample becomes smaller, the features of the Barkhausen effect are suppressed. Second, as for the successive jumps observed in the H region where the rapid change in M is entirely seen for both the samples, the number of observed M jumps for (B) is more than that for (A). Indeed, the number of the domain wall due to the 2π-soliton in the CSL increases, as the c-axis length of the single crystal increases. However, a series of M jumps must appear in a limited H region below the critical field of the order of 2 kOe. The greater the number of M jumps, the more difficult the detection of the M jump will be in the H resolution of the present setup. Thus, the effects of size on the M jumps observed in the present setup can be understood within the framework of the CSL formation. [ABSTRACT FROM AUTHOR]

The single crystal of a chiral magnet Cr1/3NbS2 exhibits discrete changes in magnetization (M) in response to changes in magnetic field (H) triggered by the formation of a chiral soliton lattice (CSL). In order to provide evidence of this phenomenon, the study of the size effect is indispensable. We investigated the effects of size on this phenomenon by the use of two single crystals, (A) and (B), whose crystal sizes along the c-axis were 110 µm and 60 µm, respectively. First, in (A), the large jumps of M observed in the process of decreasing H exhibited inconsistent features, whereas the largest and second-largest jumps in (B) exhibited reproducibility for both the value of H and the magnitude of the M jumps. This confirms that these large jumps do not originate from the Barkhausen effect, as this effect would result in M jumps appearing at random values of H. When the system size of a sample becomes smaller, the features of the Barkhausen effect are suppressed. Second, as for the successive jumps observed in the H region where the rapid change in M is entirely seen for both the samples, the number of observed M jumps for (B) is more than that for (A). Indeed, the number of the domain wall due to the 2π-soliton in the CSL increases, as the c-axis length of the single crystal increases. However, a series of M jumps must appear in a limited H region below the critical field of the order of 2 kOe. The greater the number of M jumps, the more difficult the detection of the M jump will be in the H resolution of the present setup. Thus, the effects of size on the M jumps observed in the present setup can be understood within the framework of the CSL formation. [ABSTRACT FROM AUTHOR]

We investigated the effects of hydrostatic pressure on an isotropic Nd2Fe14B magnet (the exact chemical formula is Nd2.0Fe14.1B) consisting of nanocrystals, with the size of approximately 30 nm, by magnetization measurements at pressures (P's) up to 9.3GPa and structural analyses up to 4.3GPa. Magnetization curves were measured by using a miniature diamond anvil cell made of Ti alloy with spatially uniform magnetization. The initial value of coercive field Hc at 300K is 840 kA/m (=10.6 kOe), and Hc initially increases to approximately 1180 kA/m (=15.0 kOe) almost linearly against the pressure. The increase in Hc, however, saturates at around P=3GPa. The change in Hc is understood by the decrease in the saturation magnetization Ms within the framework of the constant anisotropy of the single domain phase. The crystalline strain increases for P<1GPa. Afterward, the crystalline size (D) starts to decrease with increasing pressure, and the reduction tends to saturate at above approximately 3GPa. Furthermore, the change in Ms is actually related with both the change in strain and that in D. The data on the temperature dependence of Hc at P=0, 6.6, and 9.3GPa exhibit pressure-induced suppression of the Curie temperature. The maximum energy product decreases with increasing pressure over the whole temperature range. [ABSTRACT FROM AUTHOR]

We perform structural analysis experiments on the chiral magnet Cr1/3NbS2, in which Cr3+ ions are inserted between hexagonal NbS2 layers. The noncentrosymmetrical nature of the inserted Cr3+ appears as a distorted CrS6 octahedron. Under the application of hydrostatic pressure, the lattice shrinks significantly along the c-axis rather than the a-axis. However, at a pressure P of approximately 3-4 GPa, a kink in the rate of decrease in the lattice parameters is observed, and the slight movement of a Nb atom along the c-axis brings about a decrease in the distortion of the CrS6 octahedron. This structural change qualitatively suggests a decrease in the strength of the Dzyaloshinskii-Moriya (D-M) interaction. Under hydrostatic pressure, the magnetic ordering temperature TC decreases, and dTC/dP exhibits a slight change at around 3 GPa. A series of experiments indicates that the change in the structural symmetry of the CrS6 octahedron influences the exchange network between Cr3+ ions as well as the D-M interaction. [ABSTRACT FROM AUTHOR]

We investigated complex magnetic domain formation on a chiral molecule-based magnet, [Cr(CN)6][Mn(R)-pnH(H2O)](H2O) (termed as R-GN), whose two-dimensional molecular network was constructed with the help of a single-handed chiral ligand ((R)-pn). There, the first- and third-harmonic magnetic responses (M1ω and M3ω) against the ac magnetic field were observed, and magnetic hysteresis in ac field of a few Oe was discussed in terms of Rayleigh loop. The diagnostics of this magnetic hysteresis clarified the complex process of magnetic domain formation against a change in temperature. For R-GN, it was reported that a giant M3ω (termed #4 in this paper) appeared just above the so-called 'magnetic ordering temperature (TC).' In the present study, three M3ω responses (#1-3) were newly observed on the lower-temperature side of #4, and the ac field dependencies for all of #1-#4 were investigated. #1 also accompanied the giant M3ω, which suggests that a significant degree of magnetic fluctuation surviving below TC. This glassy behavior below TC is an attractive new phenomenon in molecule-based magnets with a single-handed chiral ligand. #2 and #3 exhibited magnetic ordering and the formation of a small magnetic domain, respectively. The M3ω responses of #1-3 were suppressed with increasing the amplitude of ac field, and the corresponding magnetic hysteresis was a normal Rayleigh loop accompanying the out-of-phase of the M1ω response. The M3ω response of #4 without the out-of-phase of M1ω was, however, enhanced with increasing the amplitude of ac field, and #4 represented a large magnetic hysteresis in the paramagnetic region, intrinsically different from those of #1-#3. [ABSTRACT FROM AUTHOR]

We applied anisotropic stress to LaMnO3+δ nanoparticles synthesized in one-dimensional pores of mesoporous silica and investigated the effects of the anisotropic strain on the nanoparticles, which consisted of ferromagnetic and antiferromagnetic particles. The nanoparticles in the one-dimensional pores were crushed without stress in the direction parallel to the silica walls that separated the pores when the mesoporous silica containing the nanoparticles is pressurized. X-ray diffraction patterns of the nanoparticles indicated that the lattice strain increased with increasing applied pressure. The lattice constants were found to reduce anisotropically, and the values saturated above a critical strain. Both the ferromagnetic and antiferromagnetic transition temperatures for the LaMnO3+δ nanoparticles initially increased with increasing pressure and then remained constant at around the critical strain. These results indicate that anisotropic stress causes distortion of the shape of nanoparticles. This induces an increase in the lattice strain and the anisotropic compression of the crystal structure, which, in turn, results in an increase in the transition temperatures. [ABSTRACT FROM AUTHOR]

It has recently been reported that, in FePt nanoparticles (NPs) protected by poly(N-vinyl-2-pyrrolidone) (PVP), which possess a particle diameter (D) near the critical size (2-3 nm) for the emergence of the face-centered tetragonal (fct) structure, the coercive field (Hc) at room temperature increases with increasing D, whereas the Hc value below 10 K increases with decreasing D. We investigated the fct-ordering parameter (S) for PVP-coated FePt NPs with three mean D values (=2.0, 2.6, and 3.4 nm) in order to gain a better insight into the unique behavior of Hc. Furthermore, the temperature dependencies of Hc, saturation magnetization (Ms), and their product (HcMs) were also investigated. The behavior of Hc at high temperature is attributed to the decrease in the magnetic switching volume (V), while the enhancement of Hc at low temperatures with decreasing D is thought to originate from the decrease in the saturation magnetization, Ms, with decreasing D. The decrease in Ms with decreasing D is related to the decrease in the fct-ordering. [ABSTRACT FROM AUTHOR]