Coexistence of ferromagnetism and superconductivity in iron based pnictides: a time resolved magnetooptical study.

Ferromagnetism and superconductivity are antagonistic phenomena. Their coexistence implies either a modulated ferromagnetic order parameter on a lengthscale shorter than the superconducting coherence length or a weak exchange coupling between the itinerant superconducting electrons and the localized ordered spins. In some iron based pnictide superconductors the coexistence of ferromagnetism and superconductivity has been clearly demonstrated. The nature of the coexistence, however, remains elusive since no clear understanding of the spin structure in the superconducting state has been reached and the reports on the coupling strength are controversial. We show, by a direct optical pump-probe experiment, that the coupling is weak, since the transfer of the excess energy from the itinerant electrons to ordered localized spins is much slower than the electron-phonon relaxation, implying the coexistence without the short-lengthscale ferromagnetic order parameter modulation. Remarkably, the polarization analysis of the coherently excited spin wave response points towards a simple ferromagnetic ordering of spins with two distinct types of ferromagnetic domains.

Multichannel photodiode detector for ultrafast optical spectroscopy.

Construction and characterization of a multichannel photodiode detector based on commercially available components with high signal to noise of ∼10(6) and a rapid frame rate, suitable for time resolved femtosecond spectroscopy with high repetition femtosecond sources, is presented.

The significance of cancer cells contaminating postoperative seroma.

Sixth postoperative day seromae of 142 breast cancer patients were searched for the presence of malignant cells. They were found in 32 patients. These patients showed significant propensity of developing distant metastases or having an unfavourable outcome of their disease although the size of their tumours was smaller than in women whose postoperative seromae were malignant-cell free. At the same time TNM tumour staging and axillary lymph node analyses failed to prove any difference between these two groups of breast cancer patients. Finally, the analyses of the state of patients' menstrual cycles showed that cycling women whose postoperative seroma contained malignant cells are at high risk of developing metastases or dying.