DC magnetization

In dc magnetic applications, an air-gap is usually required somewhere along the magnetic path of the core. In ferrite cores, the gap is placed in the center-leg of the core. The flux leaves one end of the core and flows towards the opposing end. The flux, though, repels itself and causes the flux lines to bulge out away from the centerline of the core. The presence of an air-gap creates an area... 

Magnetic studies show that the above compound is paramagnetic in nature in the temperature range 5-300 K. The magnetic susceptibility (xm) along with (Xm) vs T plots (1 Tesla) obtained from a DC-magnetization study of the powdered... 

Figure 7.2 Schematic representation of coherent oscillations between states 0) and 1) of a qubit. For an electron spin placed in a dc magnetic field, oscillations can be induced via the application of an external radio frequency (rf) pulse resonant with the Zeeman energy. The amplitude 8 of the...

The actinide SMMs discussed so far were based on uranium. In 2011, the first mononuclear transuranic SMM in the form of the Np4+ complex [Np(COT)2] (10, COT = cyclooctatetraene, C8H82-), was published [9]. Although first published in 1970, the dynamics of its magnetic moment had never been investigated. The relaxation is slow enough to be measured when applying an external dc magnetic... 

Such a system was independently realized a few years later in a completely different field driven quantum flux qubits [38]. Here, a superconducting loop can support a quantum unit of current in either direction around the loop. In an external dc magnetic field, the degeneracy of the two directions is lifted,... 

Fig. 1. Temperature dependence of the dc magnetic susceptibility of LuNi2B2C and YNi2B2C in a magnetic field of 20 Oe. ZFC and FC means zero field cooling and field cooling, respectively (after Nagarajan et al. 1994).

Observation of ESR from a particular sample is contingent upon the presence of a macroscopic spin magnetic moment jZ i.e., die sample under investigation must contain some minimum number of unpaired electron spins. Upon insertion into the cavity, the sample is subjected to the dc magnetic field H, and the unpaired electrons align themselves both parallel... 

Fig. 31 Dc-magnetic susceptibility versus temperature data for F4BImNN at 1000 Oe (a and b) magnetization versus field data at 1.8 K (c) compared to theoretical Brillouin...

Figure 14 shows the ac susceptibility data taken under non-zero dc magnetic field. As the dc field is increased, the Xm"/Xm peaks of the [Y, Tb] and [Tb, Y] complexes are shifted to higher temperatures. The shift reaches its maximum at a dc field of about 2,000 Oe. On the contrary, [Tb, Tb] does not change the positions of the two Xm"/Xm peaks. The positions of the shifted peaks of mono-Tb complexes almost coincide with the two peak of the bis-Tb complex. This clearly indicates that the two peaks of [Tb, Tb] at 27 and 20 K actually correspond to the Tbm ions at the two different sites. 

Fig. 8 The temperalure dependence of dc magnetization of (a) 3 nm and (b) 7 nm NiO nanoparticles under ZFC and FC conditions (H = 100 Oe). The inset shows the inverse susceptibility ra. temperature curves of the (a) 3 tun and (b) 7 nm particles (c) shows the data for TOPO-capped 3 nm NiO nanoparticles.

Nuclear Magnetic Resonance (NMR) [42]. When a sample (solid or liquid) consisting of nuclei of spin I and magnetization Mis placed in an external DC magnetic field H0, the Larmor frequency v0 (Hz, or cycles per second) for nuclear spin projection transitions Anti = 1 is... 

Hall voltage was measured by a four-point probe method for the samples shaped like a cross, using dc current and dc magnetic field. 

There is much interest in this superconductor for two reasons. Measurements of the effect of pressure on the material indicate that the onset transition temperature increases to 147 K when the pressure is raised to 230000 times atmospheric pressure (23.5giga Pascal). The result excited many researchers because pressure on a material can be created chemically by replacing some fraction of an ion by a similar ion of smaller radius. The obvious choice in this case was to replace the larger barium with smaller strontium. This had worked with the lanthanum compound discussed earlier. Unfortunately nature is not always so predictable. Replacement of barium by strontium reduced Tc to 127 K instead of increasing it beyond 133 K. The other reason for the interest in this material seems much more important. Resistance measurements in dc magnetic fields have shown... 

The experimental situation is inconclusive and sometimes even the same experimental techniques used by different groups give contrary results. Especially for the compounds k-(ET)2Cu(NCS)2 and K-(ET)2Cu[N(CN)2]Br many different techniques have been employed to measure A(T). Evidence for non BCS-like behavior has been obtained by complex ac susceptibility [220], radio-frequency penetration depth [221], muon spin relaxation (//SR) [222], and microwave surface impedance measurements [223]. In contrast, results consistent with conventional BCS theory, sometimes revealing a tendency towards strong coupling, are reported for measurements of the //SR [224], microwave surface impedance [225, 226], and dc magnetization [227]. 

Figure 2.34 illustrates these serious experimental problems. In the upper part (a) the magnetic penetration depth of k-(ET)2Cu(NCS)2 measured by ac susceptibility [220] and in the lower part (b) the same quantity obtained by dc magnetization [227] is shown. The clear discrepancy of the behavior of A(T) at low temperatures is obvious. In the ac-susceptibility experiment consistent with [221, 222, 223] a variation is found. This non-exponential non-BCS dependence can be explained with energy-gap nodes of several different topologies [222]. On the other hand, the data of [227] could very well be described by conventional weak-coupUng theory in the clean limit as shown... 

Fig. 2.34. Temperature dependence of the in-plane magnetic penetration depth extracted from (a) ac-susceptibility and (b) dc-magnetization measurements. The inset in (b) shows the low-T data in enlarged scale together with model curves for BCS (solid line) and for two triplet states, ti and t4 (broken curves). From [220] and [227]...

Fig. 2.35. Temperature dependence of (a) the resistivity and (b) dc magnetization of k-(ET)2Cu[N(CN)2]C1 for different applied pressures showing the reentrant behavior. From [238] and [242]...

By taking AC susceptibility of the complex over 1-1500 Hz from 1.8 to 3K, the out-of-phase susceptibility displays frequency dependence (Figure 9.26), however, none of the curves reaches a peak at 1.8 K. The DC magnetization decay method (Figure 9.26) [113, 114] determined effective barrier to be 18.4 K and a relaxation time constant of 2 x 10 s. As discussed above, Gd + is a pure spin ion the major anisotropy contribution is the Mn + ion, which is the most well known anisotropy source in the design of SMM and SCM. 

FIG. 1. Temperature dependence of the zero-field-cooled (ZFC) and field-cooled (FC) dc magnetization with a fixed applied field of 10 Oe. The mass of the sample was m —0.013 g. 

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