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Samenvatting: Het vastgoed van verblijfsgerelateerde zorginstellingen moet aan een grondige healthcheck worden onderworpen. Onderzoek van het voormalige Bouwcollege heeft onomstotelijk uitgewezen dat zeker dertig procent van de huisvesting voor intramurale zorg aan vervanging toe is. Het is duidelijk dat de kwaliteit van de huisvesting dermate te wensen overlaat, dat herontwikkeling van het zorgvastgoed nodig is. Bovendien is zorgvastgoed sinds de introductie van marktwerking en de afschaffing van de kapitaallastengarantie door de overheid noodgedwongen een nadrukkelijk onderwerp aan de bestuurderstafel.

A new experimental technique is presented to determine the intersublattice molecular-field coefficient, nRT, in heavy rare-earth-transition-metal intermetallic compounds. The technique is based on high-field magnetisation measurements on finely powdered polycrystalline material that is free to rotate in the sampleholder. Experimental results are reported for a number of Er2Fe14−xMnxB compounds. The strength of the RT exchange coupling is not affected by the Mn substitution, and a value of 0.445 Tkg/Am2has been deduced for the coefficient nRT.

The magnetic properties of the compounds Er2Fe14−xMnxhave been determined by means of X-ray diffraction, magnetic measurement and 57Fe Mössbauer spectroscopy. Magnetization measurements made in fields up to 38 T showed that the saturation moment exhibits a minimum at a Mn concentration corresponding to about x=2, due to the antiparallel coupling between the R and 3d sublattice magnetizations the latter becoming strongly reduced with increasing Mn concentration. The reduction of the 3d-sublattice magnetization is accompnied by a corresponding reduction in the 57FE hyperfine fields and by a lowering of the Curie temperature and the spin orientation temperature. Most of the compounds investigated have a break in the magnetization curves measured at 4.2 K which is interpreted as the onset of decoupling between the antiparallel rare earth and 3d sublattices. A mean field analysis was used to derive the intersublattice molecular field coefficient nRT.

The concentration dependence of the magnetic properties of Pr2Fe14−xMnxC, 0.3≤x≤10, compounds has been in Mn substitution leads to a decrease of the saturation moment, accompanied by a strong reduction of the Curie temperature. Anisotropy constants have been deduced from an analysis of high-field magnetisation isotherms at 4.2 K. First-order magnetisation processes (FOMP) have been observed.

Using a very high sensitive magnetometer the magnetization reversal of very small isolated NdFeB single crystals (μm range and below) is investigated. It turns out that similarities in the hysteresis cycle between barium ferrite single crystals and the Nd compounds can be observed. Sample size and morphology are controlled using an electron scanning microscope. While in ferrite samples of the range 1 μm single domain behaviour can be observed, the Nd2Fe14B samples still show evidence of domain wall motions.

Single crystals of Pr/sub 2/CO/sub 17/ and Nd/sub 2/Co/sub 17/ have been grown using a tri-arc Czochralski method. High-field magnetization measurements up to 35 T have been performed on Pr/sub 2/Co/sub 17/ and Nd/sub 2/Co/sub 17/ at 4.2 K. The experimental curves show very large anisotropy; for fields along the c axis in Pr/sub 2/Co/sub 17/ and along the a axis in Nd/sub 2/Co/sub 17/ the magnetization does not reach the saturation value within this field range. Furthermore, the hard axis shows in both compounds a nonzero spontaneous magnetization indicating a cone structure with cone angles of about 26 degrees and 7 degrees for Pr/sub 2/Co/sub 17/ and Nd/sub 2/Co/sub 17/, respectively. Low-field (up to 6 T) temperature-dependent magnetization measurements (4.2-300 K) show that in both compounds the cone angle remains visible up to 300 K, but for Pr/sub 2/Co/sub 17/ the cone angle is drastically reduced above 150 K. These two RE/sub 2/TM/sub 17/ compounds (RE stands for a rare-earth metal and TM stands for a transition metal) with a cone structure are compared with other RE-TM compounds with a cone structure.<>

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