Effective spin quantum numbers in iron, cobalt and nickel

✍ Scribed by U Köbler; J Englich; O Hupe; J Hesse

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 433 KB
• Volume: 339
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2003.08.116

✦ Synopsis

The known macroscopic data for the temperature dependence of the normalized spontaneous magnetization, m s ðTÞ; of iron, cobalt and nickel are reconsidered and compared with our normalized zero-field hyperfine field data, h hf ðTÞ; obtained by M .

ossbauer spectroscopy or nuclear magnetic resonance. It is observed that for all three metals h hf ðTÞ is not proportional to m s ðTÞ and systematically smaller than m s ðTÞ: This is attributed to smaller magnetic interactions in the domain walls compared to the volume of the domains. The temperature dependence of m s ðTÞ and h hf ðTÞ can be described in the whole range 0oToT C by a few temperature power functions with analytical changes (crossovers) at the intersections of these functions. Below the critical power law, m s BðT C À TÞ b ; further power functions of the absolute temperature according to m s ðTÞ ¼ A À cT e ; follow. From the observed rational exponents e it can be concluded whether the effective spin is integer or half-integer. Using additionally the known data for the saturation magnetic moments and the effective paramagnetic Bohr magneton numbers it is suggested that for nickel the effective spin is S ¼ 1=2 for T-0 but S ¼ 1 for higher temperatures including the paramagnetic phase. For iron and cobalt the corresponding values are S ¼ 3=2 and 2: