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Competition between magnetism and the kinetic energy of mobile carriers (typically holes) in doped antiferromagnets may lead to ‘stripe’ phases 1 , 2 , 3 , 4 , which are charged rivers separating regions of oppositely phased antiferromagnetism. In copper oxides the main experimental evidence for such coexisting static spin and charge order comes from neutron scattering in La 1.48 Nd 0.4 Sr 0.12 CuO 4 (LNSCO; ref.  5 ) and La 1.875 Ba 0.125 CuO 4 (LBCO; ref.  6 ). However, as a neutron is neutral, it does not detect charge but rather its associated lattice distortion 7 , so it is not known whether the stripes involve ordering of the doped holes. Here we present a study of the charge order in LBCO with resonant soft X-ray scattering (RSXS). We observe giant resonances near the Fermi level as well as near the correlated gap 8 , 9 , demonstrating significant modulation in both the doped-hole density and the ‘Mottness’, or the degree to which the system resembles a Mott insulator 10 . The peak-to-trough amplitude of the valence modulation is estimated to be 0.063 holes, which suggests 11 an integrated area of 0.59 holes under a single stripe, close to the expected 0.5 for half-filled stripes.

Pump-probe experiments and polarizing microscopy are applied to examine temperature and heat flow in metallic magnetic superlattices on glass substrates. A model of heat diffusion in thin layers for cylindrical symmetry, equivalent to the Green's function method, gives a good description of the results. The frequency dependence of temperature modulation shows that a glass layer should be added to the sample structure. The demagnetization patterns are reproduced with a Green's function that includes an interface conductance.

All-optical switching by domain wall motion has been observed in Co/Pd superlattices. Heat accumulation is part of the switching process for our experimental conditions. Numerical calculations point to a connection between domain wall motion and in-plane heat diffusion.

Time-resolved pump-probe measurements were made at variable heat accumulation in Co/Pd superlattices. Heat accumulation increases the baseline temperature and decreases the equilibrium magnetization. Transient ultrafast demagnetization first develops with higher fluence in parallel with strong equilibrium thermal spin fluctuations. The ultrafast demagnetization is then gradually removed as the equilibrium temperature approaches the Curie temperature. The transient magnetization time-dependence is fit well with the spin-flip scattering model.

Time-resolved pump-probe measurements show ultrafast and heat accumulation demagnetization in Co/Pd superlattices on glass substrates. A model of demagnetizing fields and micromagnetic simulations are applied to examine the evolution of a demagnetized cylinder into a switched state.

Resonant soft x-ray absorption measurements at the O K edge on a SrMnO3/LaMnO3 superlattice show a shoulder at the energy of doped holes, which corresponds to the main peak of resonant scattering from the modulation in the doped hole density. Scattering line shape at the Mn L3,2 edges has a strong variation below the ferromagnetic transition temperature. This variation has a period equal to half the superlattice superperiod and follows the development of the ferromagnetic moment, pointing to a ferromagnetic phase developing at the interfaces. It occurs at the resonant energies for Mn3+ and Mn4+ valences. A model for these observations is presented, which includes a double-exchange two-site orbital and the variation with temperature of the hopping frequency tij between the two sites.

X-ray absorption spectroscopy and resonant soft x-ray reflectivity show a non-uniform distribution of oxygen holes in a La2NiO4 - La2CuO4 (LNO-LCO) superlattice, with excess holes concentrated in the LNO layers. Weak ferromagnetism with Tc = 160 K suggests a coordinated tilting of NiO6 octahedra, similar to that of bulk LNO. Ni d3z2-r2 orbitals within the LNO layers have a spatially variable occupation. This variation of the Ni valence near LNO-LCO interfaces is observed with resonant soft x-ray reflectivity at the Ni L edge, at a reflection suppressed by the symmetry of the structure, and is possible through graded doping with holes, due to oxygen interstitials taken up preferentially by inner LNO layers. Since the density of oxygen atoms in the structure can be smoothly varied with standard procedures, this orbital occupation, robust up to at least 280 K, is tunable.

The superconducting transition temperature \\(T_{c}\\) of multilayers of electron-doped cuprates, composed of underdoped (or undoped) and overdoped La% \\(_{2-x}\\)Ce\\(_{x}\\)CuO\\(_{4}\\) (LCCO) and Pr\\(_{2-x}\\)Ce\\(_{x}\\)CuO\\(_{4}\\) (PCCO) thin films, is found to increase significantly with respect to the \\(T_{c}\\) of the corresponding single-phase films. By investigating the critical current density of superlattices with different doping levels and layer thicknesses, we find that the \\(T_{c}\\) enhancement is caused by a redistribution of charge over an anomalously large distance.

X-ray absorption in \\(\\rm Sr_{2}CuO_{4-\\delta}-La_{2}CuO_4\\) (SCO-LCO) superlattices shows a variable occupation with doping of a hole state different from holes doped for \\(x \\lesssim x_{optimal}\\) in bulk \\(\\rm La_{2-x}Sr_{x}CuO_4\\) and suggests that this hole state is on apical oxygen atoms and polarized in the \\(a-b\\) plane. Considering the surface reflectivity gives a good qualitative description of the line shapes of resonant soft X-ray scattering. The interference between superlattice and surface reflections was used to distinguish between scatterers in the SCO and the LCO layers, with the two hole states maximized in different layers of the superlattice.

We use resonant soft x-ray scattering (RSXS) to quantify the hole distribution in a superlattice of insulating La2CuO4 (LCO) and overdoped La_{2-x}Sr_{x}CuO4 (LSCO). Despite its non-superconducting constituents, this structure is superconducting with T_{c}=38 K. We found that the conducting holes redistribute electronically from LSCO to the LCO layers. The LCO layers were found to be optimally doped, suggesting they are the main drivers of superconductivity. Our results demonstrate the utility of RSXS for separating electronic from structural effects at oxide interfaces.