Ferromagnetic Quantum Critical Point in CePd2_2P2_2 with Pd →\rightarrow Ni Substitution

An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd$_{1-x}$Ni$_x$)$_2$P$_2$ is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature - concentration ($T-x$) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and RKKY interactions, and the introduction of disorder through alloying. Near the critical region at $x_{\rm{cr}}$ $\approx$ 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium $f$-valence crosses over from trivalent to a non-integer value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd$_2$P$_2$ has a purely trivalent cerium $f$-state, CeNi$_2$P$_2$ has a small ($<$ 10 \%) tetravalent contribution. In a broad region around $x_{\rm{cr}}$, there is a breakdown of Fermi liquid temperature dependences, signaling the influence of quantum critical fluctuations and disorder effects. Measurements of clean CePd$_2$P$_2$ furthermore show that applied pressure has a similar initial effect to alloying on the ferromagnetic order. From these results, CePd$_2$P$_2$ emerges as a keystone system to test theories such as the Belitz-Kirkpatrick-Vojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.Comment: 9 pages, 8 figure

The Lantern Vol. 6, No. 2, March 1938

• Among Our Contributors • Of Special Interest To You! • Jenny Lee • The Arguments Against Isolation • The Note • Visit of the Grandchildren • One Finds God • To The North Lies New Hampshire • The Two Camps in Washington • Substitutes • At Times It Seems So Very Strange • Episode on a Lake Shore • My Campus Song • Irony • A Chinese Mysteryhttps://digitalcommons.ursinus.edu/lantern/1017/thumbnail.jp

The Lantern Vol. 5, No. 1, December 1936

• All of Us • Public Dance • In Tibet, of All Places • Thoughts • Subterranean Conflict on the Campus • Out, Out Into Fragrance and Sweetness • My Soul Steals Out to Meet You In the Night • Bored Young Lady • Guay Shin\u27s Prayer • On Playing Ping-Pong • The Love-Life of One Cat and the Death of Another • My Lady • Danger! Germs Working! • The Wolves • Letters from India • With Apologies to Hamlet • The Dreamhttps://digitalcommons.ursinus.edu/lantern/1015/thumbnail.jp

The Lantern Vol. 4, No. 2, March 1936

• Cooperative Democracy • Fantasy • Drama: Porgy and Bess • Foreign Entanglements • The Kibitzer • My Gallery of Old Folks • My Friend, Mark Twain • Jimmy and Waffles • Reminiscence • Gold Dust • After Twenty Centuries • All the World\u27s a Stage • Early Medicinehttps://digitalcommons.ursinus.edu/lantern/1007/thumbnail.jp

The Lantern Vol. 5, No. 3, May 1937

• Dedication • Dr. McClure: An Ursinus Man • Roar, O Wind! • To the Ladies! • The Futility of Dying • The Symbolism of the British Crown • Oh! • It Might Have Been • Treat Yourself? • Three Writers • Hawaii in June • On Being a Twin • Black Magic • Triangle • Who Longs? • A Son Passes • Sing an Old-Fashioned Song • Questioning • An Argument About a Fish • That Morning Eye-Opener • Scoop for the Sun • The Dead Do Not Die Once • Give Us Timehttps://digitalcommons.ursinus.edu/lantern/1010/thumbnail.jp

The Lantern Vol. 6, No. 1, December 1937

• After Thinking Things Over • Ho! Ho! The Mistletoe! • Unrealized Dreams • Two Preeminent Victorians • The Thing • Progression • It Wasn\u27t in the Lines • He Was the Most Perfect Man • College (C)lasses • Robins and Roses • The Commuter • When the Rose is Dead • Truth in Print • Alias Mike Romanoff • Winslow Homer • When I Was Young • Maurice Evans, a Great Shakespearean • Among Our Contributors • Of Manx and Man • A Sanguinary Pirate • Conversation Has an Adventure • Ursinus\u27 Neediest Casehttps://digitalcommons.ursinus.edu/lantern/1016/thumbnail.jp

Vibrational self-trapping in beta-sheet structures observed with femtosecond nonlinear infrared spectroscopy

Self-trapping of NH-stretch vibrational excitations in synthetic Β -sheet helices is observed using femtosecond infrared pump-probe spectroscopy. In a dialanine-based Β -sheet helix, the transient-absorption change upon exciting the NH-stretch mode exhibits a negative absorption change at the fundamental frequency and two positive peaks at lower frequencies. These two induced-absorption peaks are characteristic for a state in which the vibrational excitation is self-trapped on essentially a single NH-group in the hydrogen-bonded NH⋯OC chain, forming a small (Holstein) vibrational polaron. By engineering the structure of the polymer we can disrupt the hydrogen-bonded NH⋯OC chain, allowing us to eliminate the self-trapping, as is confirmed from the NH-stretch pump-probe response. We also investigate a trialanine-based Β -sheet helix, where each side chain participates in two NH⋯OC chains with different hydrogen-bond lengths. The chain with short hydrogen bonds shows the same self-trapping behavior as the dialanine-based Β -sheet helix, whereas in the chain with long hydrogen bonds the self-trapping is too weak to be observable

Energy-Degeneracy-Driven Covalency in Actinide Bonding

Evaluating the nature of chemical bonding for actinide elements represents one of the most important and long-standing problems in actinide science. We directly address this challenge and contribute a Cl K-edge X-ray absorption spectroscopy and relativistic density functional theory study that quantitatively evaluates An–Cl covalency in AnCl62– (AnIV = Th, U, Np, Pu). The results showed significant mixing between Cl 3p- and AnIV 5f- and 6d-orbitals (t1u*/t2u* and t2g*/eg*), with the 6d-orbitals showing more pronounced covalent bonding than the 5f-orbitals. Moving from Th to U, Np, and Pu markedly changed the amount of M–Cl orbital mixing, such that AnIV 6d- and Cl 3p-mixing decreased and metal 5f- and Cl 3p-orbital mixing increased across this series