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We have investigated the magnetic ground state of a novel one-dimensional compound, NaCr 2 O 4 , in which Cr 2 O 4 double chains, i.e. zig-zag chains are aligned parallel to the b -axis, by means of both muon-spin rotation and relaxation ( μ + SR) and neutron diffraction (ND) measurements. The μ + SR results reveal the formation of static antiferromagnetic order below Neel temperature ( T N = 124 K ). The ND measurements also demonstrate the appearance of magnetic Bragg peaks with the propagation vector k → = ( 1, 0, 1 ) below T N . Combined analyses of the μ + SR and ND data clarify that the Cr moments in each zig-zag chain are aligned ferromagnetically along the c -axis, whereas antiferromagnetically along the a -axis between the adjacent zig-zag chains.

Complementary to bulk synthesis, here we propose a designer lattice with extremely high magnetic frustration and demonstrate the possible realization of a quantum spin liquid state from both experiments and theoretical calculations. In an ultrathin (111) CoCr2O4 slice composed of three triangular and one kagome cation planes, the absence of a spin ordering or freezing transition is demonstrated down to 0.03 K, in the presence of strong antiferromagnetic correlations in the energy scale of 30 K between Co and Cr sublattices, leading to the frustration factor of ∼1000. Persisting spin fluctuations are observed at low temperatures via low-energy muon spin relaxation. Our calculations further demonstrate the emergence of highly degenerate magnetic ground states at the 0 K limit, due to the competition among multiply altered exchange interactions. These results collectively indicate the realization of a proximate quantum spin liquid state on the synthetic lattice.

An $A$-type antiferromagnet, ${\mathrm{NaNiO}}_{2}$, was examined by means of positive muon spin rotation and relaxation (${\ensuremath{\mu}}^{+}\mathrm{SR}$) measurements and first-principles calculations based on a density functional theory (DFT). Below ${T}_{\mathrm{N}}=20$ K, a clear muon spin precession signal was observed in the ${\ensuremath{\mu}}^{+}\mathrm{SR}$ time spectrum recorded under zero field, due to the formation of a static internal magnetic field. The microscopic origin of such an internal field was computed as a sum of dipolar and hyperfine contact fields at the site (0.624, 0, 0.854), where both the muon site and the local spin density at such a site were predicted with DFT calculations. While the computed values were consistent with experimentally obtained ones, in both the antiferromagnetic and the paramagnetic states, the contribution of the hyperfine contact field was shown to be insignificant even below ${T}_{\mathrm{N}}$. Finally, measurements at higher temperatures signified thermally activated Na-ion diffusion with ${E}_{\mathrm{a}}=50(20)$ meV and ${D}_{\mathrm{Na}}(300\phantom{\rule{0.16em}{0ex}}\mathrm{K})=8.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}$/s, commonly observed in layered-type compounds.

Angle-resolved photoelectron spectroscopy has been used to follow the valence band and near Fermi edge electronic band structure in the quasi-1D compound NaV 2 O 4 . In this current study we have acquired the very first high-quality, high-resolution ARPES data from this material. Our data clearly reveal two distinct dispersive bands that cross the Fermi level at different k F . This is a clear signature that the electronic properties of this material is affected by the presence of a mixed valence state on the different vanadium chains and possibly also the low-temperature magnetic spin order.

QC 20211215

The microscopic magnetic nature of the $A$-site ordered chromium perovskites ${\mathrm{CaCu}}_{3}{\mathrm{Cr}}_{4}{\mathrm{O}}_{12}$ and ${\mathrm{LaCu}}_{3}{\mathrm{Cr}}_{4}{\mathrm{O}}_{12}$ and their solid-solution system, ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{Cu}}_{3}{\mathrm{Cr}}_{4}{\mathrm{O}}_{12}$, with $x=0.2$, 0.4, and 0.8, has been studied with muon spin rotation and relaxation (${\ensuremath{\mu}}^{+}\mathrm{SR}$) measurements down to 2 K using a powder sample. For ${\mathrm{CaCu}}_{3}{\mathrm{Cr}}_{4}{\mathrm{O}}_{12}$, ${\ensuremath{\mu}}^{+}\mathrm{SR}$ revealed the formation of static antiferromagnetic (AF) order below 122 K ($={T}_{\mathrm{N}}$), although magnetization measurements showed a very small change at ${T}_{\mathrm{N}}$. Analyses of the internal magnetic field ${H}_{\mathrm{int}}$ at the muon sites, predicted with first-principles calculations, suggested $G$-type AF order as a ground state. For ${\mathrm{LaCu}}_{3}{\mathrm{Cr}}_{4}{\mathrm{O}}_{12}$ with ${T}_{\mathrm{N}}=225$ K, ${\ensuremath{\mu}}^{+}\mathrm{SR}$ also supported the presence of a $G$-type AF ordered state, which was recently proposed based on neutron diffraction measurements. However, the ordered Cr moments were found to change the direction at around 10 K. For ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{Cu}}_{3}{\mathrm{Cr}}_{4}{\mathrm{O}}_{12}$, both ${T}_{\mathrm{N}}$ and ${H}_{\mathrm{int}}$ at 2 K increase monotonically with $x$.

QC 20211215

In order to elucidate the dependence of the magnetic ground state on the Ca content (x) in Sr1-xCaxCo2P2 (0 ≤x ≤1, ThCr2Si2-type structure), we have performed muon spin rotation− and relaxation (μ+SR) experiments on Sr1-xCax Co2P2 powder samples mainly in a zero applied field. The end member compound, SrCo2P2, is found to be paramagnetic down to 19 mK. As x increases, such a paramagnetic ground state is observed down to 1.8K until x = 0.45. Then, as x increases further, a short-range antiferromagnetic (AF) ordered phase appears at low temperatures for 0.48 ≤ x ≤ 0.75, and finally, a long-range AF ordered phase is stabilized for x > 0.75. The internal magnetic field of the other end member compound, CaCo2P2, is well consistent with that of the A-type AF order state, which was proposed from neutron scattering experiments. The phase diagram determined with μ+SR is different from that proposed by macroscopic measurements. For an isostructural compound, LaCo2P2, static magnetic order is found to be formed below

The magnetic nature of a novel one-dimensional compound NaCr 2 O 4 with zigzag CrO 2 chains has been studied by muon spin rotation and relaxation ( μ +SR) and neutron diffraction (ND). It is found that NaCr 2 O 4 undergoes an antiferromagnetic transition at T N = 125 K, below which the Cr moments in each zigzag chain align ferromagnetically along the c -axis but antiferromagnetically along the a -axis between adjacent zigzag chains. For the solid solution system Ca 1-x Na x Cr 2 O 4 , μ + SR measurements reveal the evolution of a complex magnetic order with increasing Ca content (1- x ), which finally enters into an incommensurate AF ordered state below T N = 21 for CaCr 2 O 4 .

As even the most cursory inspection of the contents of these summer school proceedings will reveal, muon science is extraordinarily diverse in its nature and application. Indeed the muon implantation and thermalisation processes occur so rapidly that depolarization is insignificant. This provides muon spin research (µSR) with a tremendous advantage as a magnetic resonance technique. The simplest and most familiar time-differential µSR technique is the transverse field muon spin rotation experiment, in which an external magnetic field is applied perpendicular to the muon polarization, causing the muon spins to precess about the field. If the muon polarization initially has no components perpendicular to the local field then none will develop and only the polarization along the initial direction needs to be measured. It should be noted that zero field µSR, which is generally called muon spin relaxation, is simply longitudinal field µSR in the zero field limit.

I will first review the earlyhistory of muon spin rotation/relaxation/resonance (μSR), from its origins in elementary particle physicsthrough its applications in fundamental physics, chemistry and materials science. Then I will review the more recentdevelopment of μSR facilities, modern muon beams and advanced techniques that have made μSR an indispensibletool for molecular and materials science, focusing on (but not restricted to) those pioneered at TRIUMF.

The magnetic nature of a metallic two-dimensional triangular compound, ${\mathrm{CrSe}}_{2}$, has been investigated by muon spin rotation and relaxation ($\ensuremath{\mu}^{+}\mathrm{SR}$) measurements using both powder and single crystal samples. It is found that ${\mathrm{CrSe}}_{2}$ enters into a static antiferromagnetic (AF) ordered state below 157 K ($={T}_{\mathrm{N}}$). Furthermore, the AF state is slightly changed below around 20 K ($={T}_{\mathrm{N}2}$). Based on the analysis of the internal magnetic fields at the muon sites predicted with DFT calculations, collinear AF and helical ${120}^{\ensuremath{\circ}}$ AF are clearly eliminated for the ground state of ${\mathrm{CrSe}}_{2}$. The most probable one is an incommensurate spin density wave order.

High transverse magnetic field and zero field muon spin rotation and relaxation measurements have been carried out in a lightly oxygen-doped high-${T}_{c}$ parent compound ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4}$ in a temperature range from 2 K to 300 K. As in the stoichiometric compound, muon spin rotation spectra reveal, along with the antiferromagnetic local field, the presence of an additional source of magnetic field at the muon. The results indicate that this second magnetic order is driven by the antiferromagnetism at low temperature but the two magnetic orders decouple at higher temperature. The ability of ${\ensuremath{\mu}}^{+}\mathrm{SR}$ to detect this additional magnetism deteriorates with doping, thus rendering the technique impotent to reveal time-reversal symmetry breaking in superconductors.

In order to elucidate the details of successive magnetic transitions in the rare earth cobalt arsenic oxides ( RE CoAsO), we have measured muon-spin rotation and relaxation( μ + SR) spectra of powder samples with RE = La, Ce, Pr, Nd, Sm, and Gd. Together with the result of magnetization measurements, it was found that all the compounds enter into abulk static ferromagnetic ordered phase below around 70 K(= T C ). Furthermore, additional transitions into a static antiferromagnetic ordered phase were found for the RE = Nd, Sm, and Gd compounds; namely T N1 = 15 K and T N2 = 7 K for Nd, T N1 = 41.5 K and T N2 = 17.5 K for Sm, and T N = 3K for Gd.

In order to clarify the carrier density dependence of the microscopic magnetic nature in Na x CoO 2 * y H 2 O, we have performed a μ + SR study of H 2 O and D 2 O absorbed samples. Based on the ZF- μ + SR measurements, there was no clear difference between the two superconducting phases (SCI and SCII). This is also likely to exclude the exotic scenario for the superconductivity of the SCII phase, in which the superconducting state breaks the time-reversal symmetry of the Cooper pairs, resulting in the appearance of a weak internal magnetic field below T c . Furthermore, the ZF-spectrum for the H 2 O absorbed sample exhibits a clear oscillation in the whole T range measured (1.4-100 K), suggesting the formation of “[H 3 O] + -like” H 2 μ + O ions in the sample. The absence of the oscillation in the D 2 O absorbed sample also evidences the presence of the H 2 μ + O complex. Considering the fraction of the H 2 μ + Osignal, we have demonstrated the coexistence of [H 3 O] + ions and H 2 O in this compound. Finally, the muonic Knight shift measurements suggested the change in electronic state around 10 K and 40 K for the SCI and SCII samples.

The spin-state of RECoO3(RE = La, Pr, Nd, and PrxLa1−x)has been investigated by μ+SR experiments. In particular, the muonic Knight shift in a high TF of 10 kOe was studied at temperatures below 300K. By combining these measurements with the dc-susceptibility data, the spin-state transition temperature(TSS)was found to increase monotonically as the average ionic radius of the RE ion is decreased. Our measurements demonstrate that TF-μ+SR is a unique technique to detect the spin-state transition in compounds regardless of coexistence of large magnetic moments through the change in microscopic magnetic environments at TSS.

To introduce the 12th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR), I will review some of the history of μSR, from its origins in elementary particle physics through its evolution into an essential tool of modern science, illustrating how each solution to a problem for one use of muons engenders opportunities for others.

In order to elucidate the magnetism and Li diffusion in LiFePO4, we have measured muon-spin rotation and relaxation (μ+SR) spectra for a polycrystalline LiFePO4 sample in the temperature range between 1.8 and 500K. Below TN ∼ 52K, two oscillatory signals together with onefast relaxation signal were clearly found in the zero-field (ZF) μ+SR spectrum. The three signals are reasonably explained using an antiferromagnetic (AF) spin structure proposedby neutron measurements, because electrostatic potential calculations suggests multiple different muon sites in the LiFePO4 lattice. However, the AF ordered moment estimated from μ+SR was about 3/4 of that reported by neutron, probably due to a different time window between the two techniques. In the paramagnetic state, ZF-and longitudinal-field (LF-) μ+SR spectraexhibiteda dynamic nuclear field relaxation. From the temperature dependence of the field fluctuation rate, a diffusion coeffcient of Li+ ions (DLi) at300K was estimated about 3.6×10−10 cm2/s, assuming that diffusing Li+ ions jump between the regular site and interstitial sites.

Diffusion of Li+ ionsin solidsisa basic principle behindthe operationof Li-ion batteries. Suchdiffusive behavior is represented by the diffusion equation (Fick's law), J = − D × δ ϕ/ δ x , where J is the diffusion flux, D is the self diffusion coeffcient, ϕ is the concentration, and x is the position. Although D of Li + ions( D Li)in solids is usually evaluatedby 7 Li-NMR, diffculties arise for materials that contain magnetic ions. This is because the magnetic ions contribute additional spin-lattice relaxation processes thatis considerably larger than the1/ T 1 expected from only Li diffusion [1] , [2] , [3] . This implies that 7Li-NMRprovidesa rough estimateof D Li for the positive electrode materials of Li-ion batteries, which include transition metal ions in order to compensate charge neutrality during a Li + intercala-tion/deintercalation reaction. This is an unsatisfactory situation since D Li is one of the primary parameters that govern the charge/discharge rate of a Li-ion battery. We have, therefore, attempted to measure D Li for lithium-transition-metal-oxides with muon-spin relaxation (μ + SR) since 2005 [4] , [5] , [6] . Muons do not feel fluctuating magnetic moments at high T, but instead sense the change in nuclear dipole field due to Li diffusion. Even if magnetic moments still affect the muon-spin depolarization rate, such aneffectis, in principle, distinguishablefromthatof nucleardipole fields.In particular,aweak longitudinal field can be applied that decouples the magnetic and nuclear dipole interactions [7] , [8] . Here, we wish to summarize our μ + SR study on the lithium-transition-metal-oxides, LixCoO2, LiNiO2, and LiCrO2.

In order to elucidate the structural and physical properties of the nominal composition Li[Li1/3Mn5/3]O4 compound, we have investigated the nature of polycrystalline Li[LixMn2−x]O4 (LMO) with 0 ≤ x ≤ 1/3 and Li2MnO3 samples by electrochemical charge and discharge analysis, X-ray diffraction (XRD), magnetic susceptibility (χ), and muon-spin rotation/relaxation (μSR) measurements. Here, μSR signal roughly corresponds to the volume fraction of the local magnetic phases in the sample. The Rietveld analysis suggested that the x = 1/3 sample contains ∼11 weight% Li2MnO3 phase. This was also supported by electrochemical charge and discharge analysis and zero-field (ZF-) μSR measurements. If we follow the past reported relation for the x = 1/3 compound, i.e. Li[Li1/3Mn5/3]O4 consists of a (1 − z)Li[Li1/3−ωMn5/3+ω]O4 phase and a zLi2MnO3 phase, the average chemical formula of the former spinel phase is represented as Li[Li0.21Mn1.79]O4. However, weak-transverse-field μSR measurements demonstrated that the spinel p...

The magnetism of a Pb-doped Bi 2 Sr 2 Co 2 O y (BSCO) crystal has been investigated by positive muon-spin rotation and relaxation ( μ + SR ) spectroscopy. Weak transverse field (wTF)- μ + SR measurements show that the whole sample enters into a magnetic state below ∼ 4.5 K . Combining the results of zero-field (ZF)- μ + SR experiment with susceptibility measurements, it is clarified that the sample is in a ferromagnetic ordered phase with a Curie temperature ( T C ) of 4.7 K and with the ordered internal magnetic field parallel to the c-axis within ∼ ± 15 ∘ . On the other hand, a pure BSCO crystal is also found to exhibit a bulk magnetic transition at 1.0 K by μ + SR . Since the relationship between the reduced T and reduced internal magnetic field for BSCO is almost equivalent to that for Pb-doped BSCO, the origin of the magnetic transition for both crystals is thought to be explained by common physics.

The microscopic magnetic nature of Ca 1 - x Na x V 2 O 4 with 0 ⩽ x ⩽ 1 was investigated by a positive muon-spin spectroscopy using powder samples in the T range down to 1.8 K. Static antiferromagnetic (AF) order is observed for the metallic compounds with x ⩾ 9.3 12 as well as for NaV 2 O 4 and insulating CaV 2 O 4 . A variety of phases is also found to appear as a function of x and/or temperature.

In the spin-chain compound Ca 3 CoIrO 6 muon spin precession and relaxation spectra at temperatures above 100 K exhibit non-exponential behavior characteristic of a system of dynamic, disordered magnetic moments. On cooling below about 100 K the onset of spontaneous magnetic order is revealed via the presence of coherent oscillations in muon spin relaxation spectra taken in zero external field. This magnetic transition is attributed to the intra-chain ferromagnetic order. There is one more change in the μ SR signal associated with the spin-glass like freezing transition at T f = 30 K previously established by bulk susceptibility and neutron scattering data.

The magnetic nature of the Li [ Mg x Mn 2 - x ] O 4 spinel with x = 0 , 1 8 , 1 4 , 3 8 , and 1 2 was studied by susceptibility and μ + SR measurements. As x increases from 0, T N (= 61 K) rapidly drops down to 29 K ( = T C ) for the x = 1 8 sample, and then decreases slowly with further increasing x. The sample with x = 1 2 , in which Mg 2 + and Mn 4 + ions order to form a 1:3 superlattice, exhibits a sharp ferromagnetic (FM) hysteresis below 15 K. The analysis of the ZF-spectrum implies the possibility that the FM order is incommensurate to the lattice. For the samples with 0 x 1 2 , although the lattice parameter and effective magnetic moment of Mn ions vary monotonically with x, the magnetization at 5 kOe increases in proportion to x, suggesting the existence of FM clusters probably formed by the x = 1 2 phase. Considering the results of related spinels, the cation distribution/concentration or occupancy at the octahedral site is likely to be a good indicator for the appearance of FM order in Li [ Mg x Mn 2 - x ] O 4 .

The muonic atom He 4 μ has the composition α ++ μ - e - , and is formed by stopping negative muons in He doped with a small amount of NH 3 (or Xe). It may be regarded as a unique heavy H-atom isotope with a mass of 4.1 amu. As such, the study of its chemical reaction rates and comparison with those of the well-known light Mu atom (0.113 amu) allows unprecedented tests of kinetic isotope effects over a range of 36 in mass. As a first example, and one which is of most fundamental interest, we have begun kinetics studies of the He μ + H 2 → He μ H + H reaction in the gas phase. The first measurements, at 295 K, give a rate constant of k He μ = 4.1 ± 0.7 × 10 - 16 cm 3 molec - 1 s - 1 . In comparison, variational transition state calculations give a value of 2.46 × 10 - 16 cm 3 molec - 1 s - 1 , somewhat below the measurement, despite the large error bar, raising the possibility that the calculations, on an essentially exact potential energy surface, have underestimated the amount of quantum tunneling involved, even for this heavy H-atom isotope.

In order to elucidate the nature of layered cobalt dioxides A x CoO 2 , we have investigated their microscopic magnetism by means of positive muon-spin rotation and relaxation (μ + SR) spectroscopy, in particular for A =Li, Na, and K. The dome-shaped magnetic phase diagram for Na x CoO 2 with x ⩾0.75 suggests the competition between the spin concentration and geometrical frustration on the two-dimensional triangular lattice of the CoO 2 plane. The additional experiment on Li x CoO 2 and K x CoO 2 indicates both a weakly coupled regime for the d electrons in the CoO 2 plane and an ignorable weak effect of the inter-plane interaction on their magnetic order at low T .

The magnetism for the electrochemically prepared Li x CoO 2 samples with 0.1⩽ x ⩽1 was investigated by muon-spin rotation/relaxation (μSR) and susceptibility ( χ ) measurements. The χ ( T ) curves with H =10 kOe, which correspond to the change in macroscopic magnetism, are almost T -independent down to ∼50 K for the x ⩽0.44 samples, suggesting that the samples in this x range are Pauli-paramagnetic. For the samples with 0.49⩽ x ⩽3/4, a cusp is, however, observed around 170 K in their χ ( T ) curve. Since there are no anomalies in the μSR parameters around 170 K and μSR is sensitive to local magnetic nature, the cusp is most unlikely due to a magnetic transition, but either a spin state transition or a structural phase transition. Furthermore, zero-field μSR time spectra for all the samples mainly show a slow Kubo–Toyabe behavior, indicating that muon spin is mainly depolarized by randomly oriented nuclear moments of 7 Li and 59 Co. Hence, it was clarified that all the Li x CoO 2 samples with x x CoO 2 and K x CoO 2 .

In order to elucidate the nature of layered cobalt dioxides A x CoO2, we have investigated their microscopic magnetism by means of positive muon-spin rotation and relaxation (μ+SR) spectroscopy, in particular for A = Li, Na, and K and x = 0.5. It was found that the temperature dependence of the internal antiferromagnetic field of Na0.5CoO2 (NCO) is very similar to that of K0.5CoO2 (KCO), although the former is more magnetically-anisotropic than the latter. On the other hand, Li0.5CoO2 (LCO) lacked magnetic order down to 1.7 K. The clear difference between LCO and NCO (and KCO) is likely to be caused by movement of Li+ ions in LCO, based on the zero-field μ+SR experiment.

The magnetic nature of the spinel antiferromagnet Li[Li x Mn2–x ]O4 with x = 0−0.15 has been studied with muon-spin-rotation and relaxation (μ+SR) spectroscopy. Both weak transverse field and zero field μ+SR measurements indicate that the whole sample enters into a static disordered magnetic phase below T N for all the samples measured; T N = 61 K for LiMn2O4, whereas 27–23 K for the x = 0.05−0.15 samples. It was also clarified that both the field distribution width and the field fluctuation rate show a clear change at the Jahn–Teller transition temperature (T JT = 280 K) for LiMn2O4, and a short-range cooperative JT distortion appears below 280 K even for Li[Li0.15Mn1.85]O4.

The magnetic nature of lithium insertion materials of LiNi 1− x Co x O 2 ( x = 0, 1/4, 1/2, 3/4, and 1) were investigated by means of positive muon-spin rotation/relaxation (μ + SR) spectroscopy combined with X-ray diffraction (XRD) analyses and susceptibility measurements. Zero field μ + SR spectra for all the samples below 300 K were well fitted by a dynamic Kubo–Toyabe function, indicating the existence of randomly oriented magnetic moments even at 2 K, i.e., disordered state. The field distribution width Δ due to magnetic Ni 3+ ions decreases exponentially with increasing x , suggesting that the Co substitution is likely to simply dilute Ni moments. This also supports that cobalt and nickel ions are homogeneously distributed in a solid matrix even in a muon-scale (microscopically), which is consistent with the results of macroscopic measurements.

If you’re a casual reader looking for a spellbinding page-turner, or a curious amateur technophile, this is not the book for you. It is filled with grammatical errors and clumsy diction, the tone is as dry as the Gobi Desert, and there is no graceful introduction beyond the excellent summary in the short Foreword by Albert Fert. After that the various authors plunge directly into advanced technical detail, leaving the non-expert to cope with a baffling assemblage of acronyms. The Editors have not attempted to ease this tension via any overlays of their own, being apparently content to simply assemble the authors’ completed manuscripts. If, on the other hand, you are a condensed matter physicist specializing in an area relevant to spintronics and would like to know what has been (or may be) done using the phenomena you study, or if you are an electrical engineer specializing in computing using spintronics devices, and would like a current reference handbook, or if you are a device manufacturer or a software engineer trying to anticipate the next few increments (or bypasses) of Moore’s Law, you may well find this a valuable resource. From my own viewpoint (that of a retired physicist reading for fun) this book is actually rather interesting. First because it outlines the roadblocks to Moore’s Law in meticulous detail and offers insight into where high performance computing is likely to go next; it seems quite probable that the terms of reference of Moore’s Law will be revised qualitatively before the industry bumps up against the hard limits imposed by quantummechanics and ohmic losses. Second, because it vividly displays the speciation of human endeavor in the pursuit of extremely profitable technologies: each new incremental improvement of performance (not to mention each new breakthrough) entails ever more specialized refinements of materials and techniques, leading to an encyclopedic terminology which can only fit into a finite space by reducing each to its own acronym. Here they are all assembled. One worries that verbs will be acronymized as well, so that entire sentences contain nothing but acronyms (as is common in “texting” already). But in this volume there are still many sentences recognizable as English, and some of them are quite enjoyable to read. Glossary of Acronyms: (⋆= “trending” in Spintronics)

Muon spin rotation measurements, supported by magnetization experiments, have been carried out in a stoichiometric high-${T}_{c}$ parent compound ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4}$ in a temperature range from 2 to 340 K and in transverse magnetic fields up to 5 T. Along with the antiferromagnetic local field, muon spin rotation spectra indicate the presence of an additional source of magnetic field on the muon. The characteristic splitting of about 45 G, which comes from this additional magnetic field, is consistent with spontaneous circulating currents.

The μView utility is a new Java applet version of the old db program, extended to include direct access to MUD data files, from which it can construct a variety of spectrum types, including complex and RRF-transformed spectra. By using graphics features built into all modern Web browsers, it provides full graphical display capabilities consistently across all platforms. It has the full command-line functionality of db as well as a more intuitive graphical user interface and extensive documentation, and can read and write db, csv and XML format files.

Magnetism of a misfit layered cobaltite [Ca$_2$Co$_{4/3}$Cu$_{2/3}$O$_4$]$_x^{\rm RS}$[CoO$_2$] ($x \sim$ 0.62, RS denotes a rocksalt-type block) was investigated by a positive muon spin rotation and relaxation ($\mu^+$SR) experiment. A transition to an incommensurate ({\sf IC}) spin density wave ({\sf SDW}) state was found below 180 K (= $T_{\rm C}^{\rm on}$); and a clear oscillation due to a static internal magnetic field was observed below 140 K (= $T_{\rm C}$). Furthermore, an anisotropic behavior of the zero-field $\mu^+$SR experiment indicated that the {\sf IC-SDW} propagates in the $a$-$b$ plane, with oscillating moments directed along the c axis. These results were quite similar to those for the related compound [Ca$_2$CoO$_3$]$_{0.62}^{\rm RS}$[CoO$_2$], {\sl i.e.}, Ca$_3$Co$_4$O$_9$. Since the {\sf IC-SDW} field in [Ca$_2$Co$_{4/3}$Cu$_{2/3}$O$_4$]$_{0.62}^{\rm RS}$[CoO$_2$] was approximately same to those in pure and doped [Ca$_2$CoO$_3$]$_{0.62}^{\rm RS}$[CoO$_2$], it was concluded that the {\sf IC-SDW} exist in the [CoO$_2$] planes.

We have commissioned a polarized low-energy 8 Li ion beam line, which together with a high-field β-NMR spectrometer, can act as sensitive new probe of thin films and interfaces. The implantation energy can be continuously adjusted from 1 to 90 keV and the maximum polarization achieved thus far is 80%. This instrument opens up new applications for β-NMR which parallel and complement efforts with low-energy muons. For example, it is possible to probe the magnetic field distribution near the surface of a material by stopping a polarized 8 Li beam in a thin overlayer of Ag. Since the 8 Li adopts a site with cubic symmetry in Ag there is no quadrupolar splitting of the resonance, and the 8 Li acts as a purely magnetic sensor.

To investigate the microscopic magnetic nature of phospho-olivines, we have measured positive muon-spin rotation and relaxation (${\ensuremath{\mu}}^{+}$SR) spectra for ${\mathrm{Na}}_{x}\mathrm{Fe}\mathrm{P}{\mathrm{O}}_{4}$ and $\mathrm{Fe}\mathrm{P}{\mathrm{O}}_{4}$, using powder samples in the temperature range between 2 and 200 K. For ${\mathrm{Na}}_{0.7}\mathrm{Fe}\mathrm{P}{\mathrm{O}}_{4}$, ${\ensuremath{\mu}}^{+}$SR measurements under zero external field (ZF) showed the appearance of static magnetic order below ${T}_{\mathrm{N}}\ensuremath{\sim}61$ K, at which the susceptibility $\ensuremath{\chi}(T)$ exhibits a sharp maximum due to an antiferromagnetic (AF) transition. The wide distribution found for the internal magnetic field (${H}_{\mathrm{int}}$) was reasonably explained by the formation of AF order with the spread in ${H}_{\mathrm{int}}$ due to a random distribution of Na vacancies. On the other hand, the ZF spectra for FePO${}_{4}$ suggested the formation of the canted AF order below ${T}_{\mathrm{N}}=113$ K, as proposed by neutron diffraction (ND), but the ratio between the $y$ and $x$ components of the ordered moment (${M}_{y}/{M}_{x}$) was determined as 0.6 by ${\ensuremath{\mu}}^{+}$SR, whereas 0.22 was measured by ND, probably indicating anisotropic spin fluctuations in $\mathrm{Fe}\mathrm{P}{\mathrm{O}}_{4}$.

In order to elucidate the magnetic ground state of Sr2VO4, we have measured muon spin rotation and relaxation (mu+SR) spectra of a powder sample in the temperature range between 1.8 and 140 K. As a result, we have clarified that the transition at 105 K is not magnetic but structural and/or electric in origin and found the appearance of static antiferromagnetic (AF) order below 8 K. Moreover, the distribution of the internal AF field was found to be very broad, even at the lowest temperature measured. These results are consistent with the formation of an orbital-stripe order with collinear AF order for the magnetic ground state of Sr2VO4.

For some time now, there has been considerable experimental and theoretical effort to understand the role of the normal-state “pseudogap” phase in underdoped high-temperature cuprate superconductors. Recent debate has centered on the question of whether the pseudogap is independent of superconductivity. We provide evidence from zero-field muon spin relaxation measurements in YBa 2 Cu 3 O 6+ x for the presence of small spontaneous static magnetic fields of electronic origin intimately related to the pseudogap transition. Our most significant finding is that, for optimal doping, these weak static magnetic fields appear well below the superconducting transition temperature. The two compositions measured suggest the existence of a quantum critical point somewhat above optimal doping.

In order to clarify the variation of the microscopic magnetic nature with the carrier density in Na x CoO 2 · y H 2 O , we have measured positive muon-spin rotation/relaxation ( μ + SR ) spectra for H2O as well as D2O absorbed samples. Based on the zero field (ZF-) μ + SR measurements, there was no clear difference between the two superconducting phases (SC-I and SC-II). Furthermore, the ZF-spectrum for the H2O absorbed sample exhibits a clear oscillation in the whole T range measured (1.4–100 K), suggesting the formation of “[H3O]+-like” H2μ+O ions in the sample. Further, the absence of an oscillation in the D2O absorbed sample also evidences the presence of H2μ+O. We also measured 59Co nuclear quadrupole resonance spectra of magnetic sample. The temperature dependence of spectra shows that there is no evidence of charge ordering and CDW ordering around magnetic transition temperature.

An estimate of the dimensions of the spatial distribution of the electrons involved in muonium formation in solid Ar is obtained from the dependence of the measured muonium asymmetry on applied electric field. A Monte Carlo simulation of the trajectories of electrons in the vicinity of the positive muon, assuming a simple viscous-flow model of the electron's velocities, gives dimensions of a Gaussian electron ‘cloud’ of 54(8) nm in width, length of 70(12) nm and with its centre displaced 114(10) nm upstream from the muon.

The authors present a review of recent muon spin rotation (\ensuremath{\mu}SR) studies of the vortex state in type-II superconductors. There are significant gaps in our understanding of this unusual phase of matter, especially in unconventional superconductors, for which the description of the vortex structure is a subject of great controversy. The \ensuremath{\mu}SR technique provides a sensitive local probe of the spatially inhomogeneous magnetic field associated with the vortex state. For the case of a regular vortex lattice, the magnetic penetration depth \ensuremath{\lambda} and the coherence length \ensuremath{\xi} can be simultaneously extracted from the measured internal field distribution. The penetration depth is directly related to the density of superconducting carriers in the material, and measurements of its variation with temperature, magnetic field, and impurities can provide essential information on the symmetry of the order parameter. The coherence length measured with \ensuremath{\mu}SR is the length scale for spatial variations of the order parameter within a vortex core. A primary goal of this review article is to show that measurements of these fundamental length scales are fairly robust with respect to the details of how the field distribution is modeled. The reliability of the results is demonstrated by a comparison of the \ensuremath{\mu}SR experiments with relevant theories and with other experimental techniques. The authors also review \ensuremath{\mu}SR measurements that have focused on the study of pinning-induced spatial disorder and vortex fluctuation phenomena. The \ensuremath{\mu}SR technique has proven to be a powerful tool for investigating exotic vortex phases, where vortex transitions are directly observable from changes in the \ensuremath{\mu}SR line shape. Particular emphasis is given to \ensuremath{\mu}SR experiments performed on high-temperature superconductors since high-quality single crystals have become available.

We review our recent experimental studies on delayed muonium formation in insulators and semiconductors. This involves the positive muon capturing one of the excess electrons liberated in its own ionization track and competes with recombination or escape of the electrons. The muon is generally found to thermalise well “downstream” from the center of the electron distribution, so that the transport mechanism of the electrons is a crucial factor. This is discussed in terms of the different tendencies to localization (as polarons in solids or in bubbles in liquids) vs. band‐like propagation. Studies of Van der Waals cryocrystals and cryoliquids are reviewed and some preliminary results reported for sapphire and silicon. Transport distances and times are determined from the variation of μSR signal amplitudes with applied electric and magnetic fields, respectively, enabling the development of a new technique for measuring electron mobilities on a microscopic scale.