Phase diagram of the Dzyaloshinskii-Moriya helimagnet Ba<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>CuGe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>7</mml:mn></mml:msub></mml:math>in canted magnetic fields

Mühlbauer, S.; Gvasaliya, S. N.; Ressouche, E.; Pomjakushina, E.; Zheludev, A.

doi:10.1103/physrevb.86.024417

Cited by 35 publications

(48 citation statements)

References 33 publications

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“…This crystal has already been utilized in several neutron diffraction experiments before [17,22,29]. A detailed description of the growth recipe and annealing process of the sample is given in Ref.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…[23,24] that there exists a Dzyaloshinskii vector pointing along the c axis whose sign alternates from bond to bond giving rise to weak ferromagnetism (FM), see also the discussion in Ref. [17]. As a consequence, the formation of the AFM cycloid is expected to be accompanied by the emergence of weak incommensurate FM order with the same wavevector.…”

Section: Introductionmentioning

confidence: 99%

“…Similar to MnSi [12,26], the specific heat shows a sharp latent heat which sits on top of a broader peak [17]. The origin of the first-order transition, however, has remained unclear so far.…”

Section: Introductionmentioning

confidence: 99%

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Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

et al. 2017

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Neutron diffraction on a triple-axis spectrometer and a small-angle neutron scattering instrument is used to study the magnetic phase transition in tetragonal Ba2CuGe2O7 at zero magnetic field. In addition to the incommensurate cycloidal antiferromagnetic (AFM) long-range order, we establish that weak incommensurate ferromagnetism (FM) also arises below the transition temperature TN identified by sharp Bragg peaks close to the Γ point. The intensities of both the incommensurate AFM and FM Bragg peaks vanish abruptly at TN indicative of a weak first-order transition. Above TN , evidence is presented that the magnetic intensity within the tetragonal (a, b) plane is distributed on a ring in momentum space whose radius is determined by the incommensurate wavevector of the cycloidal order. We speculate that the associated soft fluctuations are at the origin of the weak first-order transition in the spirit of a scenario proposed by Brazovskii.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

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“…The noncentrosymmetric tetragonal AF Ba 2 CuGe 2 O 7 (P 42 1 m) shows a long-range incommensurate, AF cycloidal spin spiral due to DMI below T N ≈ 3.05 K of which a number of neutron scattering studies (see, e.g., Mühlbauer et al, 2012 andZheludev et al, 1997b andRefs. therein) and theoretical work (Bogdanov et al, 2002;Chovan et al, 2013Chovan et al, , 2002 have established a quite complete understanding.…”

Section: Properties Of Non-b20 Spiral Magnets As Inferred From Sansmentioning

confidence: 99%

Magnetic small-angle neutron scattering

et al. 2019

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Small-angle neutron scattering (SANS) is one of the most important techniques for microstructure determination, being utilized in a wide range of scientific disciplines, such as materials science, physics, chemistry, and biology. The reason for its great significance is that conventional SANS is probably the only method capable of probing structural inhomogeneities in the bulk of materials on a mesoscopic real-space length scale, from roughly 1 − 300 nm. Moreover, the exploitation of the spin degree of freedom of the neutron provides SANS with a unique sensitivity to study magnetism and magnetic materials at the nanoscale. As such, magnetic SANS ideally complements more real-space and surface-sensitive magnetic imaging techniques, e.g., Lorentz transmission electron microscopy, electron holography, magnetic force microscopy, Kerr microscopy, or spinpolarized scanning tunneling microscopy. In this review article we summarize the recent applications of the SANS method to study magnetism and magnetic materials. This includes a wide range of materials classes, from nanomagnetic systems such as soft magnetic Fe-based nanocomposites, hard magnetic Nd−Fe−B-based permanent magnets, magnetic steels, ferrofluids, nanoparticles, and magnetic oxides, to more fundamental open issues in contemporary condensed matter physics such as skyrmion crystals, noncollinar magnetic structures in noncentrosymmetric compounds, magnetic/electronic phase separation, and vortex lattices in type-II superconductors. Special attention is paid not only to the vast variety of magnetic materials and problems where SANS has provided direct insight, but also to the enormous progress made regarding the micromagnetic simulation of magnetic neutron scattering.

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“…Preliminary data (not show) indicate virtually iden- tical behaviors for fields confined to the (1, 1, 0) plane [19]. For α = 5 • the propagation vector jumps by 90…”

Section: Pears the Incommensurate Peak Vanishes At H C ∼ 24 Tmentioning

confidence: 99%

Double-kphase of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O
Mühlbauer
¹
,
Gvasaliya
²
,
Pomjakushina
³

et al. 2011
Phys. Rev. B
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5
42
1
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Neutron diffraction is used to re-investigate the magnetic phase diagram of the noncentrosymmetric tetragonal antiferromagnet Ba2CuGe2O7. A novel incommensurate double-k magnetic phase is detected near the commensurate-incommensurate phase transition. This phase is stable only for field closely aligned with the 4-fold symmetry axis. The results emphasize the inadequacy of existing theoretical models for this unique material, and points to additional terms in the Hamiltonian or lattice effects. Dzyaloshinskii-Moriya (DM) antisymmetric exchange interactions [1,2] and their role in incommensurate magnetic structures are once again at the forefront of condensed matter research. One reason for the renewed interest is the discovery of novel topological skyrmion phases in the DM helimagnet MnSi and related compounds [3,4]. The other is the role that DM interactions play in certain scenarios of the multiferroic effect [5,6]. Arguably, no material has attracted more attention simultaneously in both these contexts than the tetragonal DM helimagnet Ba 2 CuGe 2 O 7 . This compound is one of the very few systems where DM helimagnetism can coexist with weak-ferromagnetic behavior [7]. Moreover, theory suggested that it can support stable skyrmions, similar to those in MnSi [7]. Ba 2 CuGe 2 O 7 has an unusual soliton lattice structure in zero field [8], and shows a very interesting behavior in applied fields [9][10][11]. While the material itself does not demonstrate spontaneous electric polarization, the isostructural and magnetically commensurate Ba 2 CoGe 2 O 7 [12, 13] is, in fact, an unconventional multiferroic material [14].The most spectacular feature of Ba 2 CuGe 2 O 7 is the commensurate-incommensurate (CI) transition that occurs in this material in applied magnetic fields [9,11]. Despite the uniqueness and fundamental importance of this compound, and years of systematic studies, its exact nature remains unresolved. Theory predicts a continuous transition with a divergent periodicity, that maps onto the classic Frenkel-Kontorova model [15]. In obvious contradiction, experiments indicate a discontinuous reorientation of spins with a poorly defined "intermediate state". The latter has been largely dismissed as a result of defect pinning [9,11], phase separation associated with a spin-flop-like discontinuous transition [16] or a poor alignment of the applied field relative to the unique 4-fold axis of the tetragonal structure [17]. In the present study we show that none of these explanations apply. In fact, the "intermediate state" is a novel double-k incommensurate phase that exists only for magnetic fields almost perfectly aligned along the 4-fold axis. Being very unlike anything predicted for this material, the double-k structure undermines all existing theoretical descriptions of Ba 2 CuGe 2 O 7 .The crystal and magnetic structures of Ba 2 CuGe 2 O 7 are reviewed in detail in Ref. 11. The magnetism is due to Cu 2+ ions that form a square lattice, cell-centered in the (a, b) plane of the tetragonal non-centric P 42 1 ...

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Phase diagram of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O7in canted magnetic fields

Cited by 35 publications

References 33 publications

Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

Magnetic small-angle neutron scattering

Double-kphase of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O
Mühlbauer
¹
,
Gvasaliya
²
,
Pomjakushina
³

et al. 2011
Phys. Rev. B
Self Cite
23
5
42
1
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Phase diagram of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O7in canted magnetic fields

Cited by 35 publications

References 33 publications

Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

Magnetic small-angle neutron scattering

Double-kphase of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2OMühlbauer1, Gvasaliya2, Pomjakushina3 et al. 2011Phys. Rev. BSelf Cite235421View full textAdd to dashboardCite

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Double-kphase of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O
Mühlbauer
¹
,
Gvasaliya
²
,
Pomjakushina
³

et al. 2011
Phys. Rev. B
Self Cite
23
5
42
1
View full text Add to dashboard Cite