Nonlinear magnetic responses at the phase boundaries around helimagnetic and skyrmion lattice phases in MnSi: Evaluation of robustness of noncollinear spin texture

The phase diagram of a cubic chiral magnet MnSi with multiple Dzyaloshinskii-Moriya (DM) vectors as a function of temperature T and dc magnetic field Hdc was investigated using intensity mapping of the odd-harmonic responses of ac magnetization (M1ω andM3ω), and the responses at phase boundaries were evaluated according to a prescription [J. Phys. Soc. Jpn. 84, 104707 (2015)]. By evaluating M3ω/M1ω appearing at phase boundaries, the robustness of noncollinear spin texture in both the helimagnetic (HM) and the skyrmion lattice (SkL) phases of MnSi was discussed. The robustness of vortices-type solitonic texture SkL in MnSi is smaller than those of both the single DM HM and chiral soliton lattice phases of a monoaxial chiral magnet Cr1/3NbS2, and furthermore the robustness of the multiple DM HM phase in MnSi is smaller than that of its SkL. Through magnetic diagnostics over the wide T -Hdc range, we found a new paramagnetic (PM) region with ac magnetic hysteresis, where spin fluctuations have been observed via electrical magnetochiral effect. The anomalies observed in the previous ultrasonic attenuation measurement correspond to the peak positions of out-of-phase M1ω. The appearance of a new PM region occurs at a characteristic magnetic field, above which indeed the SkL phase appears. It has us suppose that the new PM region could be a phase with spin fluctuation like the skyrmion gas phase

Interlayer magnetoresistance due to chiral soliton lattice formation in hexagonal chiral magnet CrNb3S6

We investigate the interlayer magnetoresistance (MR) along the chiral crystallographic axis in the hexagonal chiral magnet CrNb3S 6. In a region below the incommensurate-commensurate phase transition between the chiral soliton lattice and the forced ferromagnetic state, a negative MR is obtained in a wide range of temperature, while a small positive MR is found very close to the Curie temperature. Normalized data of the negative MR almost falls into a single curve and is well fitted by a theoretical equation of the soliton density, meaning that the origin of the MR is ascribed to the magnetic scattering of conduction electrons by a nonlinear, periodic, and countable array of magnetic soliton kinks. © 2013 American Physical Society

New magnetic intermediate state, "B - phase, " in the cubic chiral magnet MnSi

It is well known that the archetype chiral magnet MnSi stabilizes a skyrmion lattice, termed "A-phase, "in a narrow temperature range in the vicinity of the paramagnetic boundary around Tc ~29 K and Hc ~2 kOe. Recently, it has been predicted that at much lower temperatures below Tc, the conical helicoid and the forced ferromagnetic (FFM) states could be separated by a new "unknown state."In order to detect this "unknown state, "we explored the phase diagram of MnSi oriented single crystals as a function of the d.c. magnetic field (H - dc) and the temperature (T) by using a.c. magnetization measurements. For H - dc¿ , we observed a new region, termed "B-phase, "in the magnetic phase diagram, characterized by a flat-valley-like anomaly on the in-phase component of the a.c. magnetization (m'), over 3.5 = Hdc = 6.2 kOe just below the low temperature (T or , revealing that the magnetic anisotropy could play a role in the stabilization of the phase. The "B-phase"could be compatible with the theoretical predictions if the new magnetic state is supposedly related with a relative reorientation of the four helices in MnSi

Presence of a chiral soliton lattice in the chiral helimagnet MnTa3_{3}S6_{6}

Chiral helimagnetism was investigated in transition-metal intercalated dichalcogenide single crystals of MnTa$_3$S$_6$. Small-angle neutron scattering (SANS) experiments revealed the presence of harmonic chiral helimagnetic order, which was successfully detected as a pair of satellite peaks in the SANS pattern. The magnetization data are also supportive of the presence of chiral soliton lattice (CSL) phase in MnTa$_3$S$_6$. The observed features are summarized in the phase diagram of MnTa$_3$S$_6$, which is in strong contrast with that observed in other dichalcogenides such as CrNb$_3$S$_6$ and CrTa$_3$S$_6$. The presence of the remanent state provides tunable capability of the number of chiral solitons at zero magnetic field in the CSL system, which may be useful for memory device applications.Comment: 6 pages, 6 figure

Homo-chiral crystal growth and mono-chiral helimagnetism in inorganic chiral magnetic compounds

Trabajo presentado al International Workshop on Multipole Physics and Related Phenomena (J-Physics), celebrado en Hachimantai, Iwate (Japón) del 24 al 28 de septiembThis work was supported by JSPS KAKENHI Grant Number 25220803, 25390139, 26108719, 15H03680, 15H05885, 15H05886, 16KK0102, 17H02912, 17H02767, and 17H02815. JC acknowledges the Grant Number MAT2015-68200-C2-2-P from the Spanish Ministry of Economy and Competitiveness.Peer Reviewe

Presence of a chiral soliton lattice in the chiral helimagnet MnTa3S6

Chiral helimagnetism was investigated in transition-metal intercalated dichalcogenide single crystals of MnTa3S6. Small-angle neutron scattering (SANS) experiments revealed the presence of harmonic chiral helimagnetic order, which was successfully detected as a pair of satellite peaks in the SANS pattern. The magnetization data are also supportive of the presence of chiral soliton lattice (CSL) phase in MnTa3S6. The observed features are summarized in the phase diagram of MnTa3S6, which is in strong contrast with that observed in other dichalcogenides such as CrNb3S6 and CrTa3S6. The presence of the remanent state provides tunable capability of the number of chiral solitons at zero magnetic field in the CSL system, which may be useful for memory device applications

Effects of dynamic stress in magnetic superlattice of a monoaxial chiral magnet Cr1/3NbS2

A monoaxial chiral magnet forms a kind of spin superlattice structure, termed chiral soliton lattice (CSL), by the application of a magnetic field H perpendicular to a helical chiral axis. It has been reported that the CSL accompanies the magnetoresistance effect as well as a discrete change in magnetization and magnetoresistance. In order to verify the effect of the structural modification on the CSL state, we measured the magnetoresistance under the dynamic stress (DS) with a frequency of the order of MHz, which was applied by a piezoelectric ceramic oscillator. The steady application of DS while decreasing H resulted in a suppression of the insertion of chiral soliton. On the other hand, the application of a pulse-like DS while H decreased assisted the insertion of chiral soliton. These results demonstrate that DS modifies the spin structure of the monoaxial chiral magnet, and we can therefore change the activation energy for the insertion of chiral soliton while H is decreased.28th International Conference on Low Temperature Physics (LT28), 9–16 August 2017, Gothenburg, Swede

Long Periodic Helimagnetic Ordering in CrM 3S6 (M = Nb and Ta)

We report long periodic chiral helimagnetic orderings in ferromagnetic inorganic compounds CrM 3S6 (M = Nb and Ta) with a chiral space group of P6322. Magnetization in polycrystalline samples and high resolution powder neutron diffraction were measured. Our powder neutron diffraction measurements in CrM 3S6 successfully separated nuclear and magnetic satellite peaks, having the period of hundreds of angstroms along the c-axis. Therefore, we propose that the magnetic ordering in ferromagnetic CrM3S6 is not ferromagnetic, but long periodic chiral helimagnetic ordering