Mössbauer spectroscopic studies by T.SHINJO

Degree of interlayer mixing is different at the two interfaces (head and tail). A result for Fe layer in contact with Mn layer is shown here. Sample A is prepared by depositing 56 Fe(100Å)- 57 Fe(3.5Å)-Mn(100Å). While B is prepared by depositing Mn(100Å)- 57 Fe(3.5Å)- 56 Fe(100Å) A shows the situation of Mn-on-Fe, While B shows Fe-on-Mn. Spectrum for A is entirely ferromagnetic but that for B includes a large non-magnetic fraction. The result means that the mixing in Sample A is limited but a considerable mixing happened in Sample B. Such a phenomenon occurs generally if one component is rather reactive. Sample structure Spectra at RT

Spectra of ultrathin Fe layers sandwiched in MgF 2 The thinnest layer (Fe16Å) shows a decrease of hyperfine field at RT and an increase at 4K T.Shinjo et al.. Proc.Inter.Vac.Cong. (Vienne,1977)

Crystalline Amorphous M ö ssbauer spectra for Fe/Mg multilayers measured at 4K. Sample structure is [Fe(a Å)/Mg(b Å)]x50. a is from 1Å to 30Å (as indicated in the figure) while b is always 20Å ～ 30Å Results 1)Fe monoatomic layer is entirely ferromagnetic 4K. 2)Magnetization is oriented perpendicular to the film in the monolayer region and turned out to be in-plane for a > 10Å. 3)Structure of Fe layer is crystalline for a >15Å but amorphous-like for a < 12Å K.Kawaguchi et al. J.Phys.Soc.Jpn.55(1986)

y Mössbauer spectra at 4K of Fe/rare-earth multilayers. Perpendicular magnetization appears for Pr,Nd and Tb. K.Mibu and T.Shinjo, Hyper.Int. 113(1998)287.

Evidence of Fe 5+ Charge disproportionation of Fe in CaFeO3, 2Fe4+ ↔ Fe3+ + Fe5+. At 110K ～ 285K At 4K, with and without 48kOe Temp.dep.of the difference of IS(↑), and hyperfine field(←). At RT, a single line is observed, which corresponds to Fe4+. Below 280K, two isomer shifts are observed, due to the charge disproportionation. Magnetic order appears below 110K and 2 different hyperfine fields are observed at 4K. The larger one, 415kOe is close to the typical value for Fe3+. Therefore the other is attributed to Fe5+. The spectrum with applying 48kOe suggests a non-collinear spin structure. T.Shinjo et al. Ferrites, Proc.Int.Conf.Japan(1980)

Mössbauer spectrum of natural Fe at ultralow temperature (5 milli-Kelvin) Intensity of P 1 is usually equal to that of P 6, At normal temperatures, the levels A and B are equally distributed since the energy separation by the hyperfine field, 34T, is only 2mK. At ultralow temperatures, however, the Boltzmann population deviates from equal (nuclear polarization ）.. P 1 P6P6 ABAB The asymmetry of the 6-line is caused by the nuclear polarization at the ultralow temperature and P 6 /P 1 indicates the relative populations at level B and A, which is determined by H n /kT. Since the hyperfine field is 34T, the temperature can be estimated to be 5mK. T,Shinjo, Hyper.Int.42(1988)1173. Mössbauer spectrum of a natural iron foil at extremely low temperature.