Fundamentals of Nature

Researchers at the Paul Scherrer Institute PSI are looking for answers to essential questions concerning the underlying structures of matter and the fundamental principles of nature. They study the composition and properties of elementary particles – the smallest building blocks of matter – or investigate the structure of biological molecules and how they perform their function. The knowledge gathered in this way opens up new approaches to finding solutions in science, medicine and technology.

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Strain-Induced Ferromagnetism in Antiferromagnetic LuMnO3 Thin Films

Interfaces of transition metal oxides are a fertile ground for new physics, often showing novel electronic and magnetic properties that do not exist in the bulk form of the material. A relatively little-explored direction in this field concerns the interfacial properties of multifunctional materials such as the magnetoelectric multiferroics.

Diagram of the processes in the LuMnO3 layers studied. The layer is highly strained close to the substrate, which leads to a ferromagnetic (FM) order there. As the distance grows, the strain decreases so that two antiferromagnetic (AFM) orders appear: the spin spirals and the E-type, where two spins point in one direction and the next two in the other.

Strain-Induced Ferromagnetism in Antiferromagnetic LuMnO3 Thin Films

Single phase and strained LuMnO3 thin films are discovered to display coexisting ferromagnetic and antiferromagnetic orders. A large moment ferromagnetism (≈1μB), which is absent in bulk samples, is shown to display a magnetic moment distribution that is peaked at the highly strained substrate-film interface. We further show that the strain-induced ferromagnetism and the antiferromagnetic order are coupled via an exchange field, therefore demonstrating strained rare-earth manganite thin films as promising candidate systems for new multifunctional devices.

(top) Schematic view of the X-PEEM experiment with in-situ applied electric fields performed at the SIM beamline of the Swiss Light Source. (bottom) X-PEEM images of an array of nickel nanoislands showing a uniform 90° in-plane magnetization reorientation (highlighted with blue circles).

Single Domain Spin Manipulation by Electric Fields in Strain Coupled Artificial Multiferroic Nanostructures

Encoding information by the application of an electric field has a key role in the development of novel memory devices that can operate at high speed while keeping low energy consumption. In magnetoelectric multiferroics, magnetic and ferroelectric ordering coexist and are coupled together so that it is possible to manipulate the material's magnetic structure by applying an electric field with a negligible current flow.

1D to 2D Na+ Ion Diffusion Inherently Linked to Structural Transitions in Na0.7CoO2

We report the observation of a stepwise "melting" of the low-temperature Na-vacancy order in the layered transition-metal oxide Na0.7CoO2. High-resolution neutron powder diffraction analysis indicates the existence of two first-order structural transitions, one at T1 ≈ 290 K followed by a second at T2 ≈ 400 K. Detailed analysis strongly suggests that both transitions are linked to changes in the Na mobility.

RF Pulse compressor for the SwissFEL

The SwissFEL C-band (5.712 GHz) linac consists of 26 RF modules. Each module is composed of a single 50 MW klystron feeding a pulse compressor and four two meter long accelerating structures. The pulse compressor is a passive device that compresses in time the 3 μs pulse from klystron into a 330 ns pulse. The compressed power is then guided to the four accelerating structures. The pulse compressor is based on a single Barrel Open Cavity (BOC). The BOC makes use of a “whispering gallery” mode which has an intrinsically high quality factor and operates in resonant rotating wave regime (Figure 1); moreover, and contrary to the conventional SLED scheme, a single cavity is sufficient to define the pulse compressor, without the need for two cavities. A prototype has been manufactured by the Dutch company VDL (Figure 2) and successfully power tested in PSI reaching a peak power of 300 MW.

Material samples from the beam entrance window

MEGAPIE samples delivered to partners for post irradiation investigation

The MEGAWatt Pilot Experiment was operated for neutron generation with the PSI high intensity proton beam in 2006. The experiment utilized liquid target material, a lead bismuth eutectic. This marked a major milestone towards Accelerator Driven Systems (ADS), which are intended to be used for the incineration of nuclear waste.