Search

A precise measurement of the radio-purity levels of the CaWO4 crystals used for both the CRESST and the NUCLEUS experiment, is fundamental for a better background understanding. The sensitivity of HPGe detectors is not sufficient to the excellent radio-purity levels of the CaWO4 crystals produced in-house at the Technische Universität München (TUM). We report on a cryogenic α-screening facility which will provide a method to determine the radio-purity of this crystals by measuring the alpha-decays with a high precision, taking advantage of the unique experimental environment of the shallow underground laboratory (UGL) of the TUM.

The CRESST-III experiment searches for direct interactions of dark matter with ordinary matter. The main event signature would be a nuclear recoil inside one of the scintillating CaWO4 crystals. Operating the crystals as cryogenic calorimeters provides a phonon signal as measure of the deposited energy. The simultaneous readout of both signals is used to actively discriminate backgrounds. CRESST-III focuses on the sub-GeV/c2 mass region where the sensitivity is driven by the threshold. In the first data taking campaign of CRESST-III from 2016-2018 an unprecedented low threshold of 30.1 eV for nuclear recoils was obtained. In this contribution, we will report the status of the experiment and the latest results.

The spin Peltier effect (SPE) in a junction comprising a gadolinium-iron-garnet (GdIG) slab and a Pt film has been investigated around the magnetization compensation temperature of GdIG by means of the lock-in thermography method. When a charge current is applied to the Pt layer, a spin current is generated across the Pt/GdIG interface via the spin Hall effect in Pt. This spin current induces a heat current and a measurable temperature change near the Pt/GdIG interface due to the SPE. The SPE signal in the Pt/GdIG junction shows a sign change around the magnetization compensation temperature, demonstrating the similar temperature dependence of the SPE and the spin Seebeck effect for the Pt/GdIG hybrid system.

Heat capacity measurements on pure but twinned single crystals of reveal a sharp peak at , which according to thermal expansion, neutron diffraction, and magnetic susceptibility measurements originates from an antiferromagnetic ordering of the Pr-ion moments. A modest coupling to the Cu(2) spin system is observed. Below a first-order transition in the magnetic structure of the Pr spin system (at 13.4 K in warming; in cooling) is found. Field-dependent heat capacity data show anisotropic temperature dependences of the -peaks and recover a Schottky-like anomaly due to the crystal-field-split ground state of the .