Defect-correlated skyrmions and controllable generation in perpendicularly magnetized CoFeB ultrathin films

Skyrmions have attracted significant interest due to their topological spin structures and fascinating physical features. The skyrmion phase arises in materials with Dzyaloshinskii-Moriya (DM) interaction at interfaces or in volume of non-centrosymmetric materials. However, although skyrmions were generated experimentally, one critical intrinsic relationship between fabrication, microstructures, magnetization and the existence of skyrmions remains to be established. Here, two series of CoFeB ultrathin films with controlled atomic scale structures are employed to reveal this relationship. By inverting the growth order, the amount of defects can be artificially tuned, and skyrmions are shown to be preferentially formed at defect sites. The stable region and the density of the skyrmions can be efficiently controlled in the return magnetization loops by utilizing first-order reversal curves to reach various metastable states. These findings establish the general and intrinsic relationship from sample preparation to skyrmion generation, offering an universal method to control skyrmion density.

[1]  D. Mailly,et al.  Helium Ions Put Magnetic Skyrmions on the Track. , 2021, Nano letters.

[2]  Gerhard Jakob,et al.  Thermal skyrmion diffusion used in a reshuffler device , 2018, Nature Nanotechnology.

[3]  G. Durin,et al.  Individual skyrmion manipulation by local magnetic field gradients , 2019, Communications Physics.

[4]  S. Eisebitt,et al.  Field-free deterministic ultrafast creation of magnetic skyrmions by spin-orbit torques. , 2017, Nature nanotechnology.

[5]  A. Fert,et al.  Room-Temperature Current-Induced Generation and Motion of sub-100 nm Skyrmions. , 2017, Nano letters.

[6]  Kang L. Wang,et al.  Room-Temperature Skyrmion Shift Device for Memory Application. , 2017, Nano letters.

[7]  F. Buttner,et al.  Skyrmion Hall effect revealed by direct time-resolved X-ray microscopy , 2016, Nature Physics.

[8]  K. Khoo,et al.  Tunable room-temperature magnetic skyrmions in Ir/Fe/Co/Pt multilayers. , 2016, Nature materials.

[9]  A. Fert,et al.  Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature. , 2016, Nature nanotechnology.

[10]  Kang L. Wang,et al.  Direct observation of the skyrmion Hall effect , 2016, Nature Physics.

[11]  Kang L. Wang,et al.  Room-Temperature Creation and Spin-Orbit Torque Manipulation of Skyrmions in Thin Films with Engineered Asymmetry. , 2016, Nano letters.

[12]  A. Locatelli,et al.  Room-temperature chiral magnetic skyrmions in ultrathin magnetic nanostructures. , 2016, Nature nanotechnology.

[13]  A. N’Diaye,et al.  Room temperature skyrmion ground state stabilized through interlayer exchange coupling , 2015 .

[14]  Kang L. Wang,et al.  Blowing magnetic skyrmion bubbles , 2015, Science.

[15]  A. Fert,et al.  Skyrmions at room temperature : From magnetic thin films to magnetic multilayers , 2015, 1502.07853.

[16]  Benjamin Krueger,et al.  Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets. , 2015, Nature materials.

[17]  Michael D. Schneider,et al.  Dynamics and inertia of skyrmionic spin structures , 2015, Nature Physics.

[18]  T. Matsuda,et al.  Observation of the magnetic flux and three-dimensional structure of skyrmion lattices by electron holography. , 2014, Nature nanotechnology.

[19]  L. Buda-Prejbeanu,et al.  Chirality-Induced asymmetric magnetic nucleation in Pt/Co/AlOx ultrathin microstructures. , 2014, Physical review letters.

[20]  Y. Tokura,et al.  Topological properties and dynamics of magnetic skyrmions. , 2013, Nature nanotechnology.

[21]  M. O. A. Ellis,et al.  Atomistic spin model simulations of magnetic nanomaterials , 2013, Journal of physics. Condensed matter : an Institute of Physics journal.

[22]  S. Parkin,et al.  Chiral spin torque at magnetic domain walls. , 2013, Nature nanotechnology.

[23]  C. Pfleiderer,et al.  Unwinding of a Skyrmion Lattice by Magnetic Monopoles , 2013, Science.

[24]  G. Beach,et al.  Current-driven dynamics of chiral ferromagnetic domain walls. , 2013, Nature materials.

[25]  Y. Liu,et al.  Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals , 2013, Nature Communications.

[26]  C. Chien,et al.  Extended Skyrmion phase in epitaxial FeGe(111) thin films. , 2012, Physical review letters.

[27]  C. Pfleiderer,et al.  Emergent electrodynamics of skyrmions in a chiral magnet , 2012, Nature Physics.

[28]  Y. Tokura,et al.  Near room-temperature formation of a skyrmion crystal in thin-films of the helimagnet FeGe. , 2011, Nature materials.

[29]  H. Ohno,et al.  A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction. , 2010, Nature materials.

[30]  U. Nowak,et al.  Constrained Monte Carlo method and calculation of the temperature dependence of magnetic anisotropy , 2010, 1006.3507.

[31]  Y. Tokura,et al.  Real-space observation of a two-dimensional skyrmion crystal , 2010, Nature.

[32]  H. Ohno,et al.  Transmission electron microscopy investigation of CoFeB/MgO/CoFeB pseudospin valves annealed at different temperatures , 2009 .

[33]  P M Bentley,et al.  Chiral paramagnetic skyrmion-like phase in MnSi. , 2009, Physical review letters.

[34]  P. Böni,et al.  Skyrmion Lattice in a Chiral Magnet , 2009, Science.

[35]  P. Böni,et al.  Topological Hall effect in the A phase of MnSi. , 2009, Physical review letters.

[36]  E. Tsymbal,et al.  Atomic and electronic structure of the CoFeB∕MgO interface from first principles , 2006 .

[37]  O. Hellwig,et al.  Magnetization reversal of Co/Pt multilayers: Microscopic origin of high-field magnetic irreversibility - eScholarship , 2004 .

[38]  Leon Abelmann,et al.  Quantitative magnetic force microscopy on perpendicularly magnetized samples , 1998 .

[39]  Minko Balkanski,et al.  Communications in Physics , 1986 .

[40]  IEEE Transactions on Magnetics , 2022 .