1. Measurement of Grain Size of Iron Hydroxide with M ӧ ssbauer Effect Shibata lab. Yutaka Fujiwara May 27th, 2005 When iron rusts in outdoor atmosphere, grains of iron hydroxide are formed on the surface. (Graduation study at Gakushuin University) Motivation; The size of grain is related with mechanism of the rusting. We can measure grain size of iron hydroxide with M ӧ ssbauer effect. I have done solid state physics using nuclei gamma-ray.

2. Recoilless absorption of γ-ray by Fe nuclei. What is M ӧ ssbauer effect? Fe nuclei in grain are recoilless because the atomic bonding is strong. Hyperfine energy level of 57 Fe Proportional counter 57 Fe 57 Co γ-ray ( 14.4keV) Transmitted γ-ray Doppler shift Relative transmission (%) Velocity (mm/s) Energy shift (×10 -8 eV) M ӧ ssbauer spectrum of Fe

3. The sample is grain of β-FeOOH. How well can we determine the size of grain of β-FeOOH with M ӧ ssbauer spectrum? 6Å6Å O/OH Fe Grain of β-FeOOH Crystal structure of β-FeOOH β-FeOOH is iron hydroxide which is anti-ferromagnetic material.

4. T=300K Where K u =1000J/m 3 τ(ns)V(m 3 ) 41.84×10 -24 62.02×10 -24 82.21×10 -24 122.34×10 -24 1003.29×10 -24 Direction of easy magnetization axis Direction of Sublattice magnetization

5. Drastic Change of M ӧ ssbauer Spectrum. Superfine grain reverses its direction of hyper-fine field with relaxation time τ. Simulation Relaxation time Direction of easy magnetization axis Direction of Sublattice magnetization Superfine grain (nano order)

6. Reversing Hyper-fine field C = 0.1ns Relaxation time Dependence of τ on V at various temperature (K u =1000J/m 3 ) Superfine grain reverses its direction of hyper-fine field every relaxation time τ.

7. How to Analysis 測定した全ての温度について スペクトルを満足させるような体積分布を 求める 合成 分解