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Background Postoperative lymphopenia (PL) after spine surgery is reported to be an indicator of surgical-site infection (SSI). PL without SSI is often encountered, resulting in a treatment dilemma. We focused on PL, so as to improve the accuracy of detecting SSI. Methods In total, 329 patients underwent spine surgery, including nine patients presenting with SSI. The complete blood cell counts, differential counts, and C-reactive protein (CRP) level were measured pre-surgery and on postoperative days 2, 7, and 14. The relationships between PL and SSI were evaluated, and PL and non-PL conditions were compared among all cases. We then divided the patients into two groups: PL and non-PL, and determined the useful serological markers using receiver operating characteristic curves. Results Sixty-one patients presented with PL, including four with SSI. However, PL was not directly suggested as a biomarker of SSI (p = 0.067). We revealed PL as a risk factor for SSI (p = 0.004, Odds ratio: 7.54). Among all cases, the lymphocyte count and CRP level differed significantly between the PL and non-PL groups at all perioperative time-points. The white blood cell count, neutrophil count, and CRP levels on postoperative day 7 significantly differed between the SSI and non-SSI cases in the PL group. The area under the curve (AUC) for CRP was greater than that of the other parameters. The neutrophil count was only effective as a marker in the non-PL group. The combination of two cutoff values (CRP: 3.7 mg/dL (PL group) and neutrophil count: 6172/μL (non-PL group)) presented high specificity (87.2%) and sensitivity (88.9%), while only one cutoff value (CRP: 2.9 mg/dL) had a specificity of 77.4% and sensitivity of 77.8%. Conclusions Approximately one-fifth of patients developed PL post-surgery, which was a risk factor for SSI, with constant high inflammation. Grouping based on PL and establishing diagnostic cutoff values are more appropriate than establishing only one cutoff value for overall cases.

We report a combined theoretical and experimental investigation devoted to getting deeper insights into the exotic magnetic properties of the low-dimensional SeCuO3 system, for which the two inequivalent Cu(1) and Cu(2) sites show different quantum dynamics. First-principles calculations based on the density functional theory were performed to extract the magnetic exchange couplings. Briefly, we notably find that (i) the magnetic structure can be decomposed into two subsystems made of strongly antiferromagnetically coupled Cu(1) singlet state dimers and weak antiferromagnetic Cu(2) spin chains and (ii) weak ferromagnetic interactions between the two subsystems lead to magnetic frustration. The present model allows us to reproduce both mag-netic susceptibility and torque magnetometry measurements. In addition, high-magnetic-field experiments and density-matrix renormalization-group simulations evidence a half-magnetization plateau at 40-45 T associated with the polarization of the Cu(2) spin chains, while the Cu(1) dimers are expected to reach the triplet state at 210-220 T.

In materials showing a linear magnetoelectric (ME) effect, unconventional functionalities can be anticipated such as electric control of magnetism and nonreciprocal optical responses. Thus, the search for new linear ME materials is of interest in materials science. Here, using a recently proposed design principle of linear ME materials, which is based on the combination of local structural asymmetry and collinear antiferromagnetism, we demonstrate that an anion-deficient fluorite derivative, Mn3Ta2O8, is a new linear ME material. This is evidenced by the onset of magnetic-field-induced electric polarization in its collinear antiferromagnetic phase below TN = 24 K. Furthermore, we also find an antiferroelectric-like phase transition at TS = 55 K, which is attributable to an off-center displacement of magnetic Mn2+ ions. The present study shows that Mn3Ta2O8 is a rare material that exhibits both ME and antiferroelectric-like transitions. Thus, Mn3Ta2O8 may provide an opportunity to investigate the physics associated with complicated interactions between magnetic (spin) and electric dipole degrees of freedom.

In non-centrosymmetric metals, spin-orbit coupling (SOC) induces momentum-dependent spin polarization at the Fermi surfaces. This is exemplified by the valley-contrasting spin polarization in monolayer transition metal dichalcogenides (TMDCs) with in-plane inversion asymmetry. However, the valley configuration of massive Dirac fermions in TMDCs is fixed by the graphene-like structure, which limits the variety of spin-valley coupling. Here, we show that the layered polar metal BaMn$X_2$ ($X =$Bi, Sb) hosts tunable spin-valley-coupled Dirac fermions, which originate from the distorted $X$ square net with in-plane lattice polarization. We found that in spite of the larger SOC, BaMnBi$_2$ has approximately one-tenth the lattice distortion of BaMnSb$_2$, from which a different configuration of spin-polarized Dirac valleys is theoretically predicted. This was experimentally observed as a clear difference in the Shubnikov-de Haas oscillation at high fields between the two materials. The chemically tunable spin-valley coupling in BaMn$X_2$ makes it a promising material for various spin-valleytronic devices., Comment: 25 pages, 4 figures. Published in Communications Materials

Two-dimensional magnetic materials have recently attracted great interest due to their unique functions as the electric field control of a magnetic phase and the anomalous spin Hall effect. For such remarkable functions, a spin-orbit coupling (SOC) serves as an essential ingredient. Here we report a giant positive magnetoresistance in a layered magnetic semiconductor AgCrSe2, which is a manifestation of the subtle combination of the SOC and Zeeman-type spin splitting. When the carrier concentration approaches the critical value of 2.5\times10^18 cm^-3, a sizable positive magnetoresistance of ~400 % emerges upon the application of magnetic fields normal to the conducting layers. Based on the magneto-Seebeck effect and the first-principles calculations, the unconventional magnetoresistance is ascribable to the enhancement of effective carrier mass in the SOC induced J = 3/2 state, which is tuned to the Fermi level through the Zeeman splitting enhanced by the p-d coupling. This study demonstrates a new aspect of the SOC-derived magnetotransport in two-dimensional magnetic semiconductors, paving the way to novel spintronic functions., Comment: 8 papges, 5 figures

When a conduction electron couples with a non-coplanar localized magnetic moment, the realspace Berry curvature is exerted to cause the geometrical Hall effect, which is not simply proportional to the magnetization. So far, it has been identified in the case mostly where the non-coplanar magnetic order is present on the sublattice of conduction electrons. Here, we demonstrate that the geometrical Hall effect shows up even without long-range magnetic order of conduction electrons, as induced by non-coplanar exchange fields from the localized magnetic moments, in hole-doped phyrochlore molybdates. We find that the geometrical Hall effect is markedly anisotropic with respect to the applied magnetic field direction, which is in good accordance with the field-dependent magnitude and sign change of the real-space scalar spin chirality of local Tb moments. These results may facilitate the understanding of emergent electromagnetic responses induced by the Kondo-like coupling between conduction electrons and local spins in a broad material class., 9 pages, 7 figures

Quasi-zero-dimensional antiferromagnets with weakly coupled clusters of multiple spins can provide an excellent platform for exploring exotic quantum states of matter. Here, we report the synthesis and the characterization of a copper-based insulating antiferromagnet, K(NbO)Cu4(PO4)4. Single-crystal X-ray diffraction measurements reveal that the crystal structure belongs to the tetragonal space group P4/nmm, in which Cu2+ ions align to form a quasi-two-dimensional layer of spin-1/2 coupled square tetramers. The structure is quasi-isostructural to recently reported magnetoelectric antiferromagnets, A(TiO)Cu4(PO4)4 (A = Ba, Sr, and Pb) with the P4212 space group. Despite their structural similarities, whereas the antiferromagnetic transition in A(TiO)Cu4(PO4)4 produces conventional anomalies in magnetization and heat capacity, that in K(NbO)Cu4(PO4)4 has several unusual features such as an upturn in magnetic susceptibility and a very weak specific heat anomaly that corresponds to a spin entropy release as small as 3%. These results indicate that the magnetism of K(NbO)Cu4(PO4)4 is far different from that of A(TiO)Cu4(PO4)4 and suggest that the ground state is very close to a quantum nonmagnetic singlet state. The origin of the distinct magnetism in K(NbO)Cu4(PO4)4 is discussed in terms of structural modifications of a Cu4O12 unit forming a square tetramer. Our study demonstrates that the present material family, represented by an extended chemical formula A(BO)Cu4(PO4)4 (AB = KNb, BaTi, SrTi, and PbTi), has broad chemical controllability of their magnetism. This makes this system an attractive material platform to study the physics of quantum spin-1/2 coupled square tetramers.

We systematically synthesized perovskite-type oxides Sr1-xCaxCoO3 containing unusually high valence Co4+ ions by a high pressure technique, and investigated the effect of systematic lattice change on the magnetic and electronic properties. As the Ca content x exceeds about 0.6, the structure changes from cubic to orthorhombic, which is supported by the first-principles calculations of enthalpy. Upon the orthorhombic distortion, the ground state remains to be apparently ferromagnetic with a slight drop of the Curie temperature. Importantly, the compounds with x larger than 0.8 show antiferromagnetic behavior with positive Weiss temperatures and nonlinear magnetization curves at lowest temperature, implying that the ground state is noncollinear antiferromagnetic or helimagnetic. Considering the incoherent metallic behavior and the suppression of the electronic specific heat at high x region, the possible emergence of a helimagnetic state in Sr1-xCaxCoO3 is discussed in terms of the band-width narrowing and the double-exchange mechanism with the negative charge transfer energy as well as the spin frustration owing to the next-nearest neighbor interaction., Comment: 13 pages, 4 figures

High-sensitivity capacitive Faraday magnetometers were developed for static DC magnetization measurements in a sub-Kelvin region that can be used with

We performed ultrasonic measurements on (Ta$_{0.952}$V$_{0.048}$)$_2$NiSe$_5$ to investigate the contribution of acoustic phonons at the zone center to structural and possible excitonic transitions. The transverse elastic constant $C_{55}$ with irreducible representation $B_\mathrm{2g}$ exhibits softening over 90\% above a transition temperature of $T_\mathrm{s} = 280$ K, indicating the soft mode of corresponding TA phonons. Our analysis based on the quadrupole response indicates that the electron-phonon interaction contributes to the excitonic transition in addition to the hybridization between the conduction and valence bands if the excitonic transition is realized., Comment: published in JPSJ

Description, We observe magnetotransport coupled to noncoplanar spin ordering/fluctuation in a triangular-lattice magnetic semiconductor., While anomalous Hall effect (AHE) has been extensively studied in the past, efforts for realizing large Hall response have been mainly limited within intrinsic mechanism. Lately, however, a theory of extrinsic mechanism has predicted that magnetic scattering by spin cluster can induce large AHE even above magnetic ordering temperature, particularly in magnetic semiconductors with low carrier density, strong exchange coupling, and finite spin chirality. Here, we find out a new magnetic semiconductor EuAs, where Eu2+ ions with large magnetic moments form distorted triangular lattice. In addition to colossal magnetoresistance, EuAs exhibits large AHE with an anomalous Hall angle of 0.13 at temperatures far above antiferromagnetic ordering. As also demonstrated by model calculations, observed AHE can be explained by the spin cluster scattering in a hopping regime. Our findings shed light on magnetic semiconductors hosting topological spin textures, developing a field targeting diluted carriers strongly coupled to noncoplanar spin structures.

Metamagnetic transitions in the novel spin-triplet superconductor UTe$_2$ were investigated through the newly developed simultaneous measurements of magnetization and sample temperature for the field along the orthorhombic $b$-axis and close to the [011] direction, where reentrant superconductivity (RSC) is detected below and above the first-order metamagnetic transition field $H_{\rm m}$. Combining the Maxwell's relation and the Clausius-Clapeyron equation, we obtained the field dependence of Sommerfeld coefficient $\gamma$ through the first-order metamagnetic transition. A significant enhancement of the effective mass toward $H_{\rm m}$ were detected for both field directions. On the other hand, above $H_{\rm m}$, the effective mass discontinuously decreases for $H~||~b$, while it discontinuously increases for $H~||~\sim [011]$, which seems to make a crucial role for the RSC., Comment: 8 pages, 11 figures, including supplemental material. To be published in Journal of Physical Society of Japan

In materials showing a linear magnetoelectric (ME) effect, unconventional functionalities can be anticipated such as electric control of magnetism and nonreciprocal optical responses. Thus, the search for new linear ME materials is of interest in materials science. Here, using a recently proposed design principle of linear ME materials, which is based on the combination of local structural asymmetry and collinear antiferromagnetism, we demonstrate that an anion-deficient fluorite derivative, Mn

Background Chronic spontaneous urticaria (CSU) is a common mast cell-driven disease, presenting with wheals, angioedema, or both. Sleep-disordered breathing (SDB) is also a common condition and contributes to various diseases by causing chronic inflammation. Recent studies have suggested an association between CSU and SDB. Methods To determine the association between the severity of SDB and that of CSU, we studied consecutive patients with CSU who visited the Sagamihara National Hospital allergy department or dermatology department between April 1 and October 31, 2018. The severity of CSU and SDB was evaluated based on the urticaria activity score 7 (UAS7) and peripheral arterial tone apnea-hypopnea index (pAHI) derived from out-of-center sleep testing (OCST) findings, respectively; their correlation was examined. Results Of the 37 patients studied, 19 had symptom-free-to-mild CSU (UAS7 ≤15) and 18 had moderate-to-severe CSU (UAS7 ≥16). The pAHI in the latter group was significantly higher than that in the former group (18 vs. 4.2, p = 0.001). In multivariate logistic analysis, moderate-to-severe SDB (pAHI ≥15) was significantly associated with moderate-to-severe CSU even after adjusting for the BMI (adjusted odds ratio 22 [95% confidence interval, 1.7–285]). Conclusions The severity of SDB is correlated with that of CSU independently of the BMI. Physicians should consider comorbid SDB when treating patients with CSU.

When nanometric, noncoplanar spin textures with scalar spin chirality (SSC) are coupled to itinerant electrons, they endow the quasiparticle wavefunctions with a gauge field, termed Berry curvature, in a way that bears analogy to relativistic spin-orbit coupling (SOC). The resulting deflection of moving charge carriers is termed geometrical (or topological) Hall effect. Previous experimental studies modeled this signal as a real-space motion of wavepackets under the influence of a quantum-mechanical phase. In contrast, we here compare the modification of Bloch waves themselves, and of their energy dispersion, due to SOC and SSC. Using the canted pyrochlore ferromagnet Nd$_2$Mo$_2$O$_7$ as a model compound, our transport experiments and first-principle calculations show that SOC impartially mixes electronic bands with equal or opposite spin, while SSC is much more effective for opposite spin band pairs., 14 pages, 4 figures

We report the dielectric, magnetic, and ultrasonic properties of a one-dimensional organic salt $\mathrm{TTF}\text{\ensuremath{-}}{\mathrm{QBr}}_{3}\mathrm{I}$. These indicate that $\mathrm{TTF}\text{\ensuremath{-}}{\mathrm{QBr}}_{3}\mathrm{I}$ shows a ferroelectric spin-Peierls (FSP) state in a quantum critical regime. In the FSP state, coupling of charge, spin, and lattice leads to emergent excitation of spin solitons as topological defects. Amazingly, the solitons are highly mobile even at low temperatures, although they are normally stationary because of pinning. Our results suggest that strong quantum fluctuations enhanced near a quantum critical point enable soliton motion governed by athermal relaxation. This indicates the realization of quantum topological transport at ambient pressure.

STUDY DESIGN A retrospective comparative study. OBJECTIVE The aim of this study was to examine the NSD1 abnormalities in patients diagnosed with Sotos syndrome and its correlation with the presence, severity, and progression of associated scoliosis. SUMMARY OF BACKGROUND DATA Scoliosis has been reported in approximately 30% of patients diagnosed with Sotos syndrome, a genetic disorder characterized by a distinctive facial appearance, learning disability, and overgrowth. Sotos syndrome is mainly attributed to NSD1 haploinsufficiency, but with ethnical differences in genetic profile: NSD1 microdeletions are frequently identified in Japanese Sotos patients whereas intragenic mutations are more frequently found in non-Japanese patients. Although possible genotype-phenotype correlations have been proposed, the genotype of Sotos syndrome patients suffering from scoliosis has not been examined. METHODS The medical records and spinal radiographs of 63 consecutive Sotos syndrome patients at a single center were reviewed. Fluorescent in situ hybridization or microarray comparative genomic hybridization and DNA sequencing or multiplex ligation-dependent probe amplification were performed to detect 5q35 microdeletion involving the NSD1 gene and intragenic mutations of the NSD1 gene, respectively. The phenotypes of all cases and radiological assessments for the presence and progression of scoliosis were studied. RESULTS NSD1 abnormalities were identified in 55 patients (87%): microdeletion in 34 patients (54%) and intragenic mutation in 22 patients (33%). Scoliosis was observed in 26 patients (41%), with a significantly higher ratio of microdeletions than mutations. The 10 patients with progressive scoliosis all had NSD1 microdeletions. CONCLUSION Scoliosis was a common phenotypical trait in children with Sotos syndrome and its presence as well as progression were higher in cases with NSD1 microdeletions. Although all Sotos syndrome patients should be monitored for scoliosis, clinicians should be made aware that patients with NSD1 microdeletions have a higher probability of scoliosis development and progression that may require early intervention.Level of Evidence: 3.

We report on the development of a capacitance measuring system which allows measurements of capacitance in pulsed magnetic fields up to 61~T. By using this system, magnetic-field responses of various physical quantities such magnetostriction, magnetic-field-induced change in complex dielectric constant, and magneto-caloric effect can be investigated in pulsed-magnetic-field conditions. Here, we examine the validity of our system for investigations of these magnetic-field-induced phenomena in pulse magnets. For the magnetostriction measurement, magnetostriction of a specimen can be measured through a change in the capacitance between two aligned electrodes glued on the specimen and a dilatometer. We demonstrate a precise detection of valley polarization in semimetallic bismuth through a magnetostriction signal with a resolution better than 10$^{-6}$ of the relative length change. For the magnetic-field-induced change in complex dielectric constant, we successfully observed clear dielectric anomalies accompanied by magnetic/magnetoelectric phase transitions in multiferroic Pb(TiO)Cu$_4$(PO$_4$)$_4$. For the measurement of magneto-caloric effect, a magnetic-field-induced change in sample temperature was verified for Gd$_3$Ga$_5$O$_{12}$ with a capacitance thermometer made of a non-magnetic ferroelectric compound KTa$_{1-x}$Nb$_x$O$_3$ ($x$ = 0.02) whose capacitance is nearly field-independent. These results show that our capacitance measuring system is a promising tool to study various magnetic-field-induced phenomena which have been difficult to detect in pulsed magnetic fields., 10 pages, 5 figures, submitted to Review of Scientific Instruments

The physical properties of URhSn with quasi-kagome structure are studied using single-crystalline samples via electrical resistivity, magnetic susceptibility, heat capacity, thermal expansion, and high-field magnetization measurements. Remarkable magnetic anisotropy is found in the ferromagnetic (FM) state below ${T}_{\mathrm{C}}=16\phantom{\rule{4pt}{0ex}}\mathrm{K}$ as well as in the ordered state between ${T}_{\mathrm{C}}$ and ${T}_{\mathrm{O}}=54\phantom{\rule{4pt}{0ex}}\mathrm{K}$, where the easy and hard magnetization directions are the hexagonal [0001] and $[10\overline{1}0]$ axes. In the paramagnetic state, the magnetic susceptibility shows a Curie-Weiss behavior; the Weiss temperatures are positive and negative for [0001] and $[10\overline{1}0]$, respectively, indicating the presence of both FM and antiferromagnetic (AFM) correlations. The entropy release for $5f$ electrons is approximately $R\phantom{\rule{0.16em}{0ex}}\mathrm{ln}3$ at ${T}_{\mathrm{O}}$. The thermal expansion coefficient is strongly anisotropic around ${T}_{\mathrm{O}}$ between the hexagonal basal plane and the [0001] axis, indicating its remarkable anisotropic magnetoelastic response and uniaxial stress dependences. Interestingly, the magnetic field response of the higher-temperature ordered state is unusual: ${T}_{\mathrm{O}}(H)$ increases and the heat-capacity jump is enhanced with the magnetic field for $H\phantom{\rule{0.16em}{0ex}}||\phantom{\rule{4pt}{0ex}}[0001]$. Based on the established thermodynamic evidence for the second-order transition at ${T}_{\mathrm{O}}(H)$, a plausible scenario is the occurrence of a canted AFM ordering or a conical state under magnetic fields, which is stabilized when coupled with field-induced magnetic moments along the [0001] axis. Another possibility is the occurrence of quadrupole ordering at ${T}_{\mathrm{O}}(H)$.

Background The accuracy rates of several effective serological markers of surgical site infection following spine surgery are unclear. We aimed to verify the accuracy of each significant marker and identify the most suitable and effective combination of these markers for the diagnosis of surgical site infection following spine surgery. Methods This retrospective study enrolled 329 patients who underwent spine surgery for causes other than infectious spondylitis, including 9 patients with surgical site infection. Complete blood cell count, differential counts, and C-reactive protein levels were measured preoperatively and postoperatively (days 2 and 7). Serological data were compared among non-surgical site infection and surgical site infection cases. Cutoff values for items presenting significant differences were determined using receiver operating characteristic curves. Ratios in each serological factor at each time-point were compared. Combinations of these factors on postoperative day 7 and ratio items were investigated to determine the most suitable combination comprising the least number of items. Results Significant differences were noted among four factors on postoperative day 7, except for the lymphocyte count. For the ratio items, significant differences were observed among 6 items. The combination of these ten markers was examined; each factor was assigned 1 point. The most suitable combination comprising 4 items, including neutrophil count, neutrophil-to-lymphocyte ratio, lymphocyte count ratio, and C-reactive protein ratio, presented an AUC of 0.95, with a cutoff value, sensitivity, and specificity of 3 points, 0.89, and 0.92, respectively. Conclusion The combination of four markers is the most suitable criterion for the surgical site infection scoring system following spine surgery, where scores of ≥3 points strongly indicate surgical site infection. This criterion may be a strong tool for detecting surgical site infection.

Single crystals of solid solutions of ferromagnetic superconductors UCoGe and URhGe were investigated by magnetization and specific-heat measurements. These compounds behave as anisotropic ferromagnets with the easy-magnetization direction along the orthorhombic $c$ axis. The maximum Curie temperature ${T}_{C}=\phantom{\rule{0.16em}{0ex}}20\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ has been observed in $\mathrm{UC}{\mathrm{o}}_{1\ensuremath{-}x}\mathrm{R}{\mathrm{h}}_{x}\mathrm{Ge}$ for $x=0.4$. The main interest of the study was the intriguing behavior in magnetic fields applied along the $b$ axis. The temperature dependence of the $b$-axis magnetic susceptibility exhibits a maximum at a characteristic temperature ${T}_{\mathrm{max}}$. For low Rh concentrations $(xl0.4){T}_{\mathrm{max}}g{T}_{C}$ and the magnetic entropy ${S}_{\mathrm{mag}}$ at ${T}_{C}$ is very low, whereas ${T}_{\mathrm{max}}={T}_{C}$ and the ${S}_{\mathrm{mag}}$ at ${T}_{C}$ is much higher for $x\ensuremath{\ge}0.4$. A metamagneticlike anomaly in magnetization is observed in all compounds, at a critical field which appears on a similar energy scale with the value of the corresponding ${T}_{\mathrm{max}}$. The character of three paramagnetic regimes which can be distinguished in the T-$x$ and H-$x$ phase diagrams, normal, correlated, and field polarized, is discussed in relation to the field-induced reentrant superconductivity in the parent compounds.

Quasi-zero-dimensional antiferromagnets with weakly coupled clusters of multiple spins can provide an excellent platform for exploring exotic quantum states of matter. Here, we report the synthesis and the characterization of a copper-based insulating antiferromagnet, K(NbO)Cu

In noncentrosymmetric helimagnets, magnetic helices are often abruptly transformed to another magnetic structure by applying a moderate magnetic field, accompanying a variety of physical phenomena. However, antiferromagnetic (AF) helimagnets have been attracting less interest, because of the robustness to the magnetic field. Here, the authors modify an AF helimagnet to be a ferrimagnetic helimagnet, which shows an enriched magnetic phase diagram owing to competition among the spin-spin interaction, thermal fluctuations, and Zeeman coupling.

Neutron diffraction with static and pulsed magnetic fields is used to directly probe the magnetic structures in ${\mathrm{LiNiPO}}_{4}$ up to $25\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ and $42\phantom{\rule{0.16em}{0ex}}\mathrm{T}$, respectively. By combining these results with magnetometry and electric polarization measurements under pulsed fields, the magnetic and magnetoelectric phases are investigated up to $56\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ applied along the easy $c$ axis. In addition to the already known transitions at lower fields, three new ones are reported at 37.6, 39.4, and $54\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. Ordering vectors are identified with ${\mathbf{Q}}_{\mathrm{VI}}=(0,\frac{1}{3},0)$ in the interval $37.6\ensuremath{-}39.4\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ and ${\mathbf{Q}}_{\mathrm{VII}}=(0,0,0)$ in the interval $39.4\ensuremath{-}54\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. A quadratic magnetoelectric effect is discovered in the ${\mathbf{Q}}_{\mathrm{VII}}=(0,0,0)$ phase and the field dependence of the induced electric polarization is described using a simple mean-field model. The observed magnetic structure and magnetoelectric tensor elements point to a change in the lattice symmetry in this phase. We speculate on the possible physical mechanism responsible for the magnetoelectric effect in ${\mathrm{LiNiPO}}_{4}$.