Mixed-valent manganites are noted for their unusual magnetic, electronic and structural phase transitions. For example, the La(1-x)Ca(x)MnO(3) phase diagram shows that below transition temperatures in the range 100-260 K, compounds with 0.2 < x < 0.5 are ferromagnetic and metallic, whereas those with 0.5 < x < 0.9 are antiferromagnetic and charge ordered. In a narrow region around x = 0.5, these totally dissimilar ground states are thought to coexist. It has been shown that charge order and charge disorder can coexist in the related compound, La(0.25)Pr(0.375)Ca(0.375)MnO(3). Here we present electron microscopy data for La(0.5)Ca(0.5)MnO(3) that shed light on the distribution of these coexisting phases, and uncover an additional, unexpected phase. Using electron holography and Fresnel imaging, we find micrometre-sized ferromagnetic regions spanning several grains coexisting with similar-sized regions with no local magnetization. Holography shows that the ferromagnetic regions have a local magnetization of 3.4 +/- 0.2 Bohr magnetons per Mn atom (the spin-aligned value is 3.5 micro (B) per Mn). We use electron diffraction and dark-field imaging to show that charge order exists in regions with no net magnetization and, surprisingly, can also occur in ferromagnetic regions.

Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures 1, 2 . While they are commonly portrayed as two dimensional objects, in reality magnetic skyrmions are thought to exist as elongated, tube-like objects extending through the thickness of the sample 3, 4 . The study of this skyrmion tube (SkT) state is highly relevant for investigating skyrmion metastability 5 and for implementation in recently proposed magnonic computing 6 . However, direct experimental imaging of skyrmion tubes has yet to be reported. Here, we demonstrate the first real-space observation of skyrmion tubes in a lamella of FeGe using resonant magnetic x-ray imaging and comparative micromagnetic simulations, confirming their extended structure.The formation of these structures at the edge of the sample highlights the importance of confinement and edge effects in the stabilisation of the SkT state, opening the door to further investigations into this unexplored dimension of the skyrmion spin texture.Skyrmion states are typically stabilised by the interplay of the ferromagnetic exchange and Zeeman energies with the Dzyalohsinskii-Moriya Interaction (DMI) 7 . In ferromagnet/heavy metal multilayer thin films, interfacial DMI is induced by symmetry-breaking spin-orbit coupling at the interface between the layers, leading to the formation of Néel-type skyrmions [8][9][10] . Bulk DMI, arising due to the lack of centrosymmetry in the underlying crystal lattice, is responsible for the formation of Bloch-type skyrmions in a range of chiral ferromagnets [11][12][13][14][15] . In crystals of these bulk materials the skyrmion state is typically only at equilibrium in a limited range of applied magnetic field and temperature just below the Curie temperature, T c , forming a hexagonal skyrmion lattice (SkL) in a plane perpendicular to the applied magnetic field.2 Figure 1 | Visualisation of the skyrmion tube spin texture. Three dimensional visualisation of three magnetic skyrmion tubes from the micromagnetic simulations presented in this paper, illustrating their extended spin structure. The inset highlights the location of the magnetic Bloch point at the end of each skyrmion tube. 3The three dimensional visualisation in Fig. 1 depicts the extended spin structure of three magnetic skyrmion tubes. The dynamics of this skyrmion tube (SkT) state play an important role in the creation and annihilation of skyrmions. For example, metastable skyrmions, which are created beyond the equilibrium thermal range by rapid field cooling 16 , are thought to unwind into topologically trivial magnetic states through the motion of a magnetic Bloch point located at the end of each individual skyrmion tube 3, 5 . Real-space observation of this dimension of the SkT state and its associated dynamics requires an in-plane magnetic field applied perpendicular to the imaging axis. Electron imaging techniques such as Fresnel Lorentz Transmission Electron Microscopy (LTEM) 12, 13 , and elec...

2. The concept of a skyrmion was introduced in 1961 in the context of nuclear physics [2] and in 1989, magnetic skyrmions were predicted [3] to occur as a result of the competition between the Heisenberg exchange energy and the Dzyaloshinskii-Moriya interaction. [4] We use the term "DMskyrmions" to refer to such objects.DM-skyrmions were found experimentally [5] in bulk MnSi in 2009. This prompted the recent intense research effort as

Modulations in manganites attributed to stripes of charge/orbital/spin order are thought to result from strong electron-lattice interactions that lock the superlattice and parent lattice periodicities. Surprisingly in La1-xCaxMnO3 (x>0.5,90 K), convergent beam (3.6 nm spot) electron diffraction patterns rule out charge stacking faults and indicate a superlattice with uniform periodicity. Moreover, large area electron diffraction peaks are sharper than simulations with stacking faults. Since the electron-lattice coupling does not lock the two periodicities (to yield stripes) it may be too weak to strongly localize charge.

We introduce a new class of isolated three-dimensional skyrmion that can occur within the cone phase of chiral magnetic materials. These novel solitonic states consist of an axisymmetric core separated from the host phase by an asymmetric shell. These skyrmions attract one another. We derive regular solutions for isolated skyrmions arising in the cone phase of cubic helimagnets and investigate their bound states.PACS numbers: 75.30. Kz, 12.39.Dc, The Dzyaloshinskii-Moriya (DM) interaction in noncentrosymmetric magnets is a result of their crystallographic handedness 1 and is responsible for the formation of long-range modulations with a fixed sense of the magnetization rotation 1,2 and the stabilization of two-dimensional axisymmetric localized structures called skyrmions 3,4 . Long-range homochiral modulations (helices) were found in the noncentrosymmetric cubic ferromagnet MnSi several decades ago and since then, other cubic ferromagnets with B20 structures have been investigated intensively 5-7 as have other chiral magnetic materials 8,9 . Isolated chiral skyrmions have been discovered recently in PdFe/Ir(111) nanolayers with induced DM interactions and strong easy-axis anisotropy 10-12 .Chiral skyrmions are two-dimensional topological solitons with an axisymmetric structure localized in nanoscale cylindrical regions. They exist as ensembles of weakly repulsive particles in the saturated phase of noncentrosymmetric magnets 4,13,14 in which all the atomic spins are parallel to an applied magnetic field. In cubic helimagnets, below a certain critical field, H D , the saturated phase transforms into the chiral helical state with the propagation direction along the applied field called the cone phase 2 . Unlike the saturated phase, the boundary values imposed by the longitudinal modulations of the cone phase violate a rotational symmetry of the system, and are thus incompatible with the axisymmetric arrangement of skyrmions investigated in Refs. 4, 10, 11, and 13. Then, the question arises: "are there any localized states compatible with the encompassing cone phase?"In our report we address this compatibility problem and derive regular solutions for asymmetric skyrmions embedded into the cone phase. We demonstrate that unlike the repulsive axisymmetric skyrmions existing in the saturated states, chiral solitons in the cone phase have an attractive interskyrmion potential and form biskyrmion and multiskyrmion states.We consider the standard model for magnetic states in (color online). Magnetic structure of an isolated skyrmion in the cone phase: calculated contour plots of mz(x, y) in three layers with ∆ψc = 2π/3. Details of the magnetization distribution are given in Fig. 2. cubic non-centrosymmetric ferromagnets 1,2 ,where m = (sin θ cos ψ; sin θ sin ψ; cos θ) is the unity vector along the magnetization M, A is the exchange stiffness constant, D is the Dzyaloshinskii-Moriya (DM) coupling energy, and H is the applied magnetic field.Chiral modulations along the applied field with the period L D = 4πA/|D| correspon...