Electron Spin Resonance in Ferromagnetic Sc3+xIn Alloys

Abstract

We report the observation of electron spin resonance (ESR) in ferromagnetic Sc3+xIn. This material shows a strong narrow peak in the total magnetization as a function of x, with ferromagnetism occurring at low temperatures for x in the range of 0.10–0.20. We have studied the ESR properties of thin polycrystalline plates for several values of x lying both within and also outside the ferromagnetic region. Measurements were made at 12 and 18 GHz as a function of temperature. The temperature range extended from 1.3 to 50 K (several times the maximum Curie temperature, Tc, of 7 K). The g-value (corrected for demagnetization effects) is 2.02±0.01 at 1.4 K and appears to decrease to approximately 1.99 at the highest observable temperatures. The minimum linewidth occurs at Tc and increases slightly at lower temperatures. For T>Tc the line broadens rapidly with increasing temperatures. A comparison of the ESR linewidth with the reciprocal of the total magnetization as a function of temperature shows that even though both have the same qualitative type of behavior, the quantitative agreement is not as good as that predicted by the theory of exchange enhancement of spin lifetimes. Although one might normally expect a rather fast relaxation rate for the electrons of such an alloy, it appears that the small g-shift and a form of exchange enhancement are important for substantially increasing spin lifetimes and producing narrow lines at low temperatures.

Electron spin resonance of magnetic materials in high fields and high frequencies

“…The line width shows a minimum near T. and steeply increases above it. This behavior is quite different from that of Ni metal [20], but similar to the case of other itinerant ferromagnets, Sc 3 In [21] and ZrZn2 [22]. The broad width for the para- magnetic state is supposed to be due to strong correlations of the d-band electrons, although a detailed calculation has not been published.…”

Evidence for exchange enhancement of TiBe2 from ESR

“…We have not so far an explanation for the behaviour of the line width in the whole temperature region. It is clear that Walsh et al formula [8] for the life time enhancement factor does not hold (except may be for the low temperature region) in agreement also with the results in ScIn3 [9], mentioned earlier, that failed to show a quantitative agreement. Beuneu and Monod [7] have recently investigated the Elliot relation by plotting the known experimental data of DH/p as a function of ~g2 for all the metal elements where the CESR has been published.…”

“…Within this paramagnetic picture it is possible to analyse our data along the same lines as has already been followed for Pd [7], ZrZn2 [8] and ScIn3 [9]. At first we give an approximate determination of the exchange enhancement factor : by writing :…”

“…It is derived on the assumption that the relaxation is towards the instantaneous magnetization and it agrees with Brinkman and Engelsberg [11] results at low temperatures. They have used this model to explain their line width result in the itinerant ferromagnet ZrZn2 in its paramagnetic state, but in a very limited region 30 K to 60 K. The same procedure in the itinerant ferromagnet ScIn3 has failed to give a quantitative agreement [9]. In both cases the temperature dependent contribution to the relaxation due to phonons in the presence of the spin-orbit coupling was not included.…”

Spin Dynamics of (Sc $$_{1-x}$$ 1 - x Lu $$_{x}$$

“…For investigating the spin dynamics of itinerant magnets, the technique of electron spin resonance (ESR) has proven to be a powerful tool [ 3 – 5 ], since the exchange enhancement of spin-lifetimes enables strong and narrow lines [ 6 , 7 ]. Early ESR results on Sc In reveal a spin resonance with a lineshape typical for itinerant resonant spins [ 8 ]. An investigation of the ESR in (Sc Lu ) In should, in principle, enable us to observe how changing the ferromagnetic correlations with Lu substitution influences the linewidth.…”