Nobuyuki Iwata

Magnetic ordering of rare earth ions and magnetic-electric interaction of hexagonal RMnO3 (R=Ho, Er, Yb or Lu)

From magnetic, dielectric and magnetoelectric measurement, it is concluded that hexagonal HoMnO 3 , ErMnO 3 and YbMnO 3 undergo a magnetic phase transition at a low temperature where a magnetic lon...

Electric and Magnetic Low-Temperature Phase Transitions of YbMn2O5.

We made measurements of dielectric constant, pyroelectric current, magnetic susceptibility and magnetoelectric effect of single crystals of YbMn 2 O 5 . From the results, we concluded that there were two phase transitions besides antiferromagnetic transition at approximately 40 K. The first transition at 32 K is characterized by a peak of dielectric constant, a kink of magnetoelectric polarization and an appearance of pyroelectricity below this temperature. It was considered to be electric in nature. The second one is at 6 K. It is also accompanied by another peak of dielectric constant, a steep rise of pyroelectricity and anomalies of both magnetic and magnetoelectric susceptibilities. We suppose that the ordering of Yb 3+ magnetic moments begins to develop at this temperature, involving a change in the crystal structure and then in spontaneous polarization. The low temperature phase has a magnetic field-induced transition which occurs at about 19 kOe at 4.2 K.

Preparation and magnetic properties of EuO thin films epitaxially grown on MgO and SrTiO3 substrates

Ferromagnetic EuO films were epitaxially grown on MgO and SrTiO 3 substrates aligned with EuO[100]//MgO[100], EuO(001)//MgO(001) and EuO[100]//SrTiO 3 [110], EuO(001)//SrTiO 3 (001). The single pha...

Magnetoelectric effect of TmMn2O5

Abstract Based on the measurements of pyroelectricity, dielectric constant, magnetization and magnetoelectric effect, we conclude that TmMn2O5 is ferroelectric below the Curie temperature of 36 K. There are two other transitions at 26 K and 6 K. The phase below 6 K undergoes a transition into another phase at about 5 kOe, possibly the reorientation of the Tm3+ moments. The dielectric properties change remarkably at this transition, indicating a strong interaction between electric and magnetic orders. Magnetic phase diagram at low temperatures is determined from the results of magnetic and dielectric measurement.

Magnetic-field-induced transition of thulium manganese oxide TmMn2O5

Abstract We report the magnetic field dependence of dielectric constant and magnetoelectric effect of TmMn2O5 and YbMn2O5 single crystals. An anomalous change of magnetoelectric effect occurs at 5 kOe (TmMn2O5) or at 18 kOe (YbMn2O5) at 4.2 K, when an magnetic field is applied along the c-direction. The anomaly in YbMn2O5 is attributed to a transition between different magnetic structures. In TmMn2O5 an anomaly was also observed in dielectric constant. We propose a structural transition caused by a magnetic field.

Magnetoelectric effect and rare earth magnetic ordering of ErMnO3

Abstract We made dielectric, magnetic and magnetoelectric studies of a hexagonal ErMnO3. Our purpose is to make clear the magnetic-electric interaction phenomena expected in this oxide with both electric and magnetic long range ordering. The magnetic-electric interaction was demonstrated as the anomalies of dielectric constant along the polar axis at magnetic transitions. An additional spontaneous polarization and a large magnetoelectric effect were detected at low temperatures where a long range ordering of Er3+ moments was present.

Preparation and Characterization of EuO/BaO Bilayer Epitaxially Grown on SrTiO 3 Substrate

We grew epitaxially single phase ferromagnetic EuO film on SrTiO 3 substrate by inserting BaO buffer layer with an orientation of EuO[100]//BaO[100]//SrTiO 3 [110] and EuO(001)//BaO(001)//SrTiO 3 (001). Compared with EuO film on MgO substrate, high quality of the film was obtained, demonstrated by appearance of Kikuchi line in RHEED pattern with less thickness, Laue oscillations around EuO(002) Bragg peak, lower full width of half maximum of rocking curve for EuO(002), and lower coercive field. The growth rate of EuO was between 8.0×10 -2 and 2.6×10 -1 A· s -1 , depending on the growth condition. Saturation magnetic moment 6.84(±0.31)µ B was obtained per europium atom. The oxygen deficiency of EuO film was estimated as less than 0.03% from the temperature dependence of resistivity. The highest resistivity detected was 2.55×10 11 Ω· cm at 83.8 K.

Observations of Flux Penetration in High-Temperature Superconductors Using Magneto-Optical Effect of EuO Layer

Fenomagnetic oxide EuO is a promising candidate for magneto-optical layer to investigate the flux penetration in high-temperature superconductors. EuO has the Curie temperature of 69K. Au film of 1 μm was deposited on EuO film as a reflection and protection layer. The magnetic moments of Eu2+ were ordered in plane. We have succeeded for the first time in observing the magneto-optical images of distribution of magnetic flux in NdBa2Cu3O7-δ single crystal using EuO film, at 5K up to 5.5T and at 60K up to 2.2T.