Magnetic phase diagram of Ni(NO3)2 6NH3

The magnetic phase diagram of Ni(NO₃)₂6NH₃ was determined from the field and temperature dependence of the magnetic susceptibility. The zero temperature exchange and anisotropy fields were determined to be H_E(0) ≈ 26 kOe and H_A(0) ≈ 0.7 kOe respectively.     

Magnetic properties of CeB6 single crystal

Magnetic measurements of CeB₆ have been made in fields up to 80 kOe at temperatures up to 1000 K. Below 2.3 K, each magnetization vs field curve shows several critical points depending on the direction of field, but between 2.3 and 3 K, the curve is smooth. Above about 3 K, the magnetization curve has a break point at a certain field which increases monotonically with increasing temperature. The paramagnetic susceptibility has been analysed by assuming appropriate values of crystal-field splitting and exchange interactions. From these results, a magnetic phase diagram for CeB₆ has been proposed.     

Magnetic characteristics of R6Mn23 hydrides (R = Gd,Ho or Er)

R₆Mn₂₃ systems, with R = Gd, Ho and Er, were hydrided to the composition R₆Mn₂₃H_x where x ap; 22. Magnetic properties of these systems and the parent intermetallics were studied over the temperature range 4 to 300 K and at applied field up to 21 kOe. Since Y₆Mn₂₃H₂₅ was established earlier to exhibit only Pauli paramagnetism, the magnetism of the R₆Mn₂₃ hydrides must originate with the rare earth sublattice. Gd₆Mn₂₃H₂₂ orders at ≈ 150 K, whereas ordering in Gd₆Mn₂₃ occurs at 468 K. The moment measured at 4 K indicates a non-collinear structure, perhaps generated by competition involving exchange between nearest and next nearest neighbors. The hydrides involving Ho and Er appear to remain paramagnetic to the lowest temperatures studied, perhaps because the reduced de Gennes factor exchange is insufficient to produce magnetic ordering. The possibility cannot be excluded, however, that they are antiferromagnetic.     

Magnetic properties of the intermetallic compound Ce5Ge4

Magnetic and magnetocaloric properties of the compound Ce₅Ge₄ have been studied. This compound has orthorhombic Sm₅Ge₄-type structure (space group Pnma, no. 62) and orders ferromagnetically at ~12 K (T_C). The paramagnetic Curie temperature is ~−20 K suggesting the presence of competing ferromagnetic and antiferromagnetic interactions in this compound. The magnetization does not seem to saturate even in fields of 90 kOe at 3 K consistent with the presence of competing interactions. Saturation magnetization value (extrapolated to 1/H→0) of only 0.8μ_B/Ce³⁺ is obtained compared to the free ion value of 2.14μ_B/Ce³⁺. This moment reduction in the ordered state of Ce₅Ge₄ could be due to partial antiferromagnetic/paramagnetic ordering of the Ce moments and may also be due to crystalline electric field effects. Magnetic entropy change near T_C, calculated from the magnetization vs. field data, is found to be moderate with a maximum value of ~9 J/kg/K at ~11 K for a field change of 90 kOe.     

Magnetic properties of A DyNi2 single crystal

Magnetic measurements have been performed on a single crystal of DyNi₂ in applied fields up to 135 kOe. In the ferromagnetic range (T_c = 25 K), the easy magnetization direction is [100] and the hardest one is [111]. Crystal field parameters have been determined from the field and temperature dependence of the magnetization measured along the three principal axes. A two-dimensional model has been used to take into account the rotation of magnetization towards the field. The deduced parameters are W = -0.8 K and x = 0.49. The corresponding anisotropy is very large: especially even a field of 135 kOe applied along a difficult magnetization axis cannot rotate the magnetization along this direction.     

Magnetic phase transitions,anisotropic susceptibility and dipolar interactions in antiferromagnetic MnNb2O6

The magnetic properties of MnNb₂O₆ single crystals have been studied in the temperature range 1.6–300 K (T_N = 4.4 K), in fields up to 220 kOe. The high field saturation at low temperature, as well as the paramagnetic susceptibility at high temperature, agree well with a ${}^6\text{S}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ state for Mn²⁺ ions. From 1.6 to 3.8 K a spin flop is induced by fields ranging from 17 to 21 kOe, applied in the direction of the a-axis. Elements of the magnetic susceptibility tensors up to rank 12, measured below the spin flop field, are in accordance with a magnetic anisotropy originating mainly from magnetic dipolar interactions.     

Magnetic characteristics of PrCd single crystal

Magnetic measurements have been made along the [100], [110] and [111]-axes of PrCd single crystal in magnetic fields up to 70 kOe in the temperature range from 4.2 to 300 K. PrCd shows metamagnetism below T_t = 25 K in which two critical fields are observed in the magnetization processes along the [110] and [111]-axes and a critical field along the [100]-axis. The metamagnetic behaviour is interpreted by a noncollinear antiferromagnetic model with the Pr moments of ～ 2μ_B directed to the 〈111〉-axes.     

Effect of the magnetic field on the 3d ordering and on the spin correlations of the linear antiferromagnet TMMC

The effect of an external magnetic field in the range 6–47 kOe on the low temperature proton spin-lattice relaxation rate in TMMC has been investigated. A peak in T₁^?1 at the 3d ordering temperature has been detected. Values of T_N for fields up to 47 kOe have been determined.     

Strange anisotropy in amorphous metals

The spin orientation in ferromagnetic amorphous Fe₈₃P₅C₁₂ in an external magnetic field, H_ext, applied perpendicular to the ribbon sample has been determined by magnetoresistance measurements and by the angular dependence of the hyperfine interaction. In small fields, H_ext ? 4 kOe, the spins tend to orient themselves perpendicular to H_ext due to the influence of the demagnetizing field and in large fields, H_ext ≈ 50 kOe, a complete alignment was not obtained.     

Magnetic and structural phase transitions in YMn<Subscript>2</Subscript>O<Subscript>5</Subscript> ferromagnetoelectric crystals induced by a strong magnetic field

Magnetic, magnetoelectric, and magnetoelastic properties of YMn₂O₅ ferromagnetoelectric single-crystals are investigated in strong pulsed magnetic fields of up to 250 kOe and in static magnetic fields of up to 12 kOe. It is found that, in YMn₂O₅ at T < T_N=42 K, a transverse weakly ferromagnetic moment of σ ₀=0.8 G cm³/g exists that is oriented along axis a and is attributed to the magnetoelectric interaction. When a magnetic field is directed along axis b, which is likely to be the axis of antiferromagnetism, a spin-flop transition is observed that is accompanied by jumps in magnetostriction and electric polarization. When a magnetic field is directed along axis a, the temperature of ferroelectric transition shifts from 20 to 25 K at H≈200 kOe. A theoretical analysis of the experimental results is given within phenomenological theory with regard to the fact that a YMn₂O₅ compound belongs to noncollinear antiferromagnetic crystals even in the exchange approximation.     

A Mössbauer effect study of the magnetic ordering in the Y6(FexMn1−x)23 solid solutions

The ternary alloys, Y₆ (Fe_xMn_1–2)₂₃, exhibit interesting magnetic behavior over a range of solid solutions of iron and manganese. The transition metal atoms occupy four crystallographically different sites. For x less than ca. 0.27, the transition metal atoms couple ferromagnetically, whereas for greater values of x they couple antiferromagnetically. By using the iron populations for each site, obtained from neutron diffraction studies, it is possible to determine the Mössbauer effect hyperfine parameter fields for each site. As x increases, the ordering temperature decreases dramatically. At 1.3K in Y₆Fe₂₃, the four hyperfine fields range from 372kOe to 250kOe, whereas in Y₆(Fe_0.52Mn_0.48)₂₃ they decrease to values between 100kOe and 10kOe. This decrease apparently results from the increasing frustration of the ferromagnetic iron-iron coupling as additional manganese, which would prefer antiferromagnetic coupling, is introduced into the alloys.     

Magnetic phase diagrams of Mn(Nb0.5Ta0.5)2O6

The magnetic phase diagrams of Mn(Nb_0.5Ta_0.5)₂O₆ have been determined by means of neutron diffraction. Two spin-flop-transitions G_xA_z → A_xG_z → G_y have been detected in a magnetic field parallel to the x-direction. The first phase boundary increases as the temperature rises up to a triple point at 4.74 K and 20.5 kOe, whereas the second phase boundary decreases until another triple point at 4.55 K and 35.5 kOe is reached. In fields parallel to the z-direction a transition G_xA_z → G_xG_z has been revealed, the phase boundary meets the paramagnetic one in a triple point at 4.65 K and 55 kOe.     

Paramagnetic Meissner effect at high fields in YCaBaCuO single crystal and melt-textured YBaCuO

We report on systematic field-cooled magnetization experiments in an Y_0.98Ca_0.02Ba₂Cu₃O_7?δ single crystal and melt-textured YBa₂Cu₃O_7?δ samples. Magnetic fields up to 50 kOe were applied and a paramagnetic response related to the superconducting state was observed. We discuss our results in terms of the flux compression scenario into the sample.     

The first experimental evidence of a field-induced magnetic phase transition in an S = 1 singlet ground state system

A magnetic phase transition to a long range ordered state is observed in Ni(C₅H₅NO)₆(ClO₄)₂ in external fields 26.4 kOe< H < 71.0 kOe applied parallel to the threefold axis and below temperatures of 0.80 K.     

Magneto-optical measurement on the layer type magnet (CH2)2(ND3)2MnCl4

The linear birefringence (LB) of the antiferromagnet (CH₂)₂(ND₃)₂MnCl₄ has been measured as a function of temperature and in magnetic fields up to 100 kOe. The temperature dependence of the LB points to a pronounced two dimensional magnetic behaviour. No anomaly corresponding to the effect of three dimensional ordering could be detected at T_N. In theffield dependent measurements the spin flop at H_SF = 33.6 ± 1 kOe (T = 4K) could clearly be detected.     

Electronic specific heat and high field magnetization studies on the Y6(Fe1−xMnx)23 system

Magnetizations at applied fields up to 120 kOe and electronic specific heats have been determined for ternaries represented by the formula Y₆(Fe_1?xMn_x)₂₃. The Curie temperature and ordered magnetic moment of Y6Mn₂₃ and Y₆Fe₂₃ decrease sharply when these materials are formed into solid solutions, being minimal in the vicinity of the equimolal solution. To test whether the reduction is a band effect electronic specific heats were measured; they are maximal where T_c and the moment are minimal, indicating unimportance of band effects. Curie-Weiss behavior is exhibited at low fields, suggesting rather localized d-electrons. The nearest neighbor distances are such as to lead to antiferromagnetic Mn-Mn interactions. Y₆Mn₂₃ is taken to be ferrimagnetic whereas Y₆Fe₂₃ appears to be ferromagnetic. While the magnetic structure of the ternaries is yet to be fully clarified, it is clear that antiferromagnetic exchange is enhanced when either binary is formed into a ternary. It also appears that the Mn-Fe coupling is antiferromagnetic in the ternaries.     

Research on the magnetic properties and crystal lattice aberrance of melt-spun Nd9Fe85−xMnxB6 (x=0–1)

Magnetic properties and crystal lattice aberrance of melt-spun Nd₉Fe_85−xMn_xB₆ (x=0,0.5,1) nanocomposite materials were investigated by DTA, XRD, EXAFS and VSM. It was found that a certain amount of manganese added to Nd₉Fe₈₅B₆ magnets can promote crystal and enhances the hard magnetic properties. The coercivity and remanence ratio increases from 4.3 kOe and 0.70 to 5.0 kOe and 0.72, respectively. The remain magnetization has not distinct reduce under the optimum annealing method. M–T shows Mn doping decreases the Curie temperature of the Nd₂Fe₁₄B phase and raises that of α-Fe phase. The origin for the enhancement of magnetic properties is not only related to the reduction of grain size which enhances the exchange coupling between grains but also to the precise crystal structure.     

Giant magnetoresistance and kinetic phenomena in <Emphasis Type="Italic">n</Emphasis>-Ag<Subscript>4</Subscript>SSe in the vicinity of a phase transition

Isotropic giant negative magnetoresistance (from ?42 to ?52%) in magnetic fields of 6–9 kOe is revealed for the first time when studying kinetic phenomena and the magnetoresistive effect in silver sulfoselenide (n-Ag₄SSe) in the vicinity of a first-order phase transition. The electron transport and the magnetoresistive effect in n-Ag₄SSe are studied for the first time.     

Magnetoresistance and magnetic phase transitions in a Pr11B6 antiferromagnet

In isotopically pure praseodymium hexaboride (Pr¹¹B₆) single-crystal samples, the transverse magnetoresistance Δρ/ρ has been measured in a temperature range of 2–20 K in magnetic fields up to 80 kOe. The field and angular dependences Δρ/ρ(H, ?, T ₀) reveal a new magnetic phase in the AFM state of Pr¹¹B₆ which is observable only for the external magnetic field orientation in a narrow angular range near H ‖ 〈110〉. The data remove the previous contradictions in the Pr11B6 magnetic phase diagram representation and can be explained under the assumption that the spin-polarized regions (ferrons) are involved in the formation of the complex magnetic structure in the Pr¹¹B₆ AFM state in the 5d band in the vicinity of the rare-earth ions.     

57Fe and 166Er Mössbauer and magnetic studies of RFe4B (R = Er,Tm, Lu) compounds

Magnetic and Mössbauer studies have been carried out on a series of ternary borides RFe₄B (R = Er, Tm, Lu) which have the hexagonal CeCo₄B type structure. These compounds are found to be magnetically ordered at room temperature. Magnetization studies in the temperature range from 5 to 300 K reveal the presence of compensation temperatures in Er and Tm compounds and indicate antiferromagnetic coupling between the rare earth and Fe moments. Room temperature ⁵⁷Fe Mössbauer studies yield values of hyperfine fields at the two Fe sites as 246 and 185 kOe in ErFe₄B and TmFe₄B, and 204 and 145 kOe in LuFe₄B. The ¹⁶⁶Er Mössbauer studies give nearly free-ion hyperfine field at the Er sites which indicates that the exchange interaction in ErFe₄B is much stronger than crystal field interaction.