Journal of Magnetism and Magnetic Materials 272–276 (2004) e1623–e1625 NMR in pulsed high magnetic fields J. Haase a, *, D. Eckert b , H. Siegel b , K.-H. M . uller b , H. Eschrig b , A. Simon c , F. Steglich a a Max Planck Institute for Chemical Physics of Solids, Noethnitzer Str. 40, Dresden 01187, Germany b Leibniz Institute for Solid State and Materials Research Dresden, P.O. Box 270116, Dresden 01171, Germany c Max Planck Institute for Solid State Research, Heisenbergstrasse 1, Stuttgart 70569, Germany Abstract The first, direct observation of nuclear magnetic resonance (NMR) in strong pulsed fields is reported. Examples of 63 Cu NMR from copper metal at 300 K and fields up to 33 T show that the sensitivity and resolution obtainable are sufficient for its use as spectroscopy at the highest fields available, as well as a field diagnostic tool. r 2003 Elsevier B.V. All rights reserved. PACS: 67.80.Jd; 82.56.b Keywords: NMR; Pulsed field Pulsed field magnets are being used increasingly to perform physical property measurements in the highest available fields [1,2]. Special conditions arising from available space and the time-dependent field increase the number of obstacles for experiments. This seems to apply to nuclear magnetic resonance (NMR), in particular. A not very well known, time-dependent, inhomogeneous magnetic field prevents NMR signal averaging, and with a repetition time of almost 30 min (necessary for the main magnet coil to cool down again) there seems almost no room for any calibration or optimization procedure necessary for finding the in- herently weak NMR signal. On the other hand, pulsed high-field magnets are the source for the highest available fields that will be out of reach of ordinary NMR for many years to come, and NMR would be beneficial as a spectroscopic tool for high-field physics. For these reasons we set out to investigate the feasibility of performing NMR in pulsed high-field magnets. While there are various choices for exploratory test samples, we chose Cu metal. Here, one has to use a powder to avoid signal loss from the small radio frequency (RF) penetration depth, a few mm: The fine (B10 mm) powder was mixed with epoxy resin to avoid electrical contact among the grains. When one estimates the signal-to-noise ratio of 63 Cu for a 25 mm 3 sample, one finds that at 9 T it should be bigger than 10 3 (at 300 K and a bandwidths of about 1 MHz). Uncertain- ties come from the filling factor of the coil, as well as the oxidation of the Cu grain surfaces and associated quadrupole broadening. Nevertheless, it should be possible to observe the signal in a single-shot experi- ment. Since a probe and a new, portable spectrometer had to be built we decided to perform all necessary tests using our static 9 T magnet where 63 Cu ðI ¼ 3 2 Þ reso- nates at around 100 MHz: An advantage of using Cu is the presence of 65 Cu ðI ¼ 3 2 Þ that has a 7:13% larger gyromagnetic ratio (the abundance of 63 Cu and 65 Cu is 0.69 and 0.31, respectively) whose resonance allows for an independent test. With the RF probe we aimed at a bandwidth of 1–2 MHz; a frequency range in which a p=2-pulse for Cu can be accomplished easily for a 25 mm 3 sample (less than 200 W of RF power). This gives us a search window of greater than 1–2% putting less constraint on reaching a particular field strength with great precision. The RF coil formed a parallel resonance with a fixed capacitor. The driving impedance for the circuit of 50 O; the same as the characteristic impedance of the ARTICLE IN PRESS *Corresponding author. Institute for Solid State and Materials Research, P.O. Box 270116, Dresden 1171, Germany. Tel.: +49-351-4659-524; fax: +49-351-4659-313. E-mail address: m.wolf@ifw-dresden.de (J. Haase). 0304-8853/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.951