Artificial control of the bias-voltage dependence of tunnelling anisotropic magnetoresistance using quantization in a single-crystal ferromagnet

A major issue in the development of spintronic memory devices is the reduction of the power consumption for the magnetization reversal. For this purpose, the artificial control of the magnetic anisotropy of ferromagnetic materials is of great importance. Here, we demonstrate the control of the carrier-energy dependence of the magnetic anisotropy of the density of states (DOS) using the quantum size effect in a single-crystal ferromagnetic material, GaMnAs. We show that the mainly two-fold symmetry of the magnetic anisotropy of DOS, which is attributed to the impurity band, is changed to a four-fold symmetry by enhancing the quantum size effect in the valence band of the GaMnAs quantum wells. By combination with the gate-electric field control technique, our concept of the usage of the quantum size effect for the control of the magnetism will pave the way for the ultra-low-power manipulation of magnetization in future spintronic devices.Comment: 9 pages, 7 figure

Anomalous Fermi level behavior in GaMnAs at the onset of ferromagnetism

We present the systematic study of the resonant tunneling spectroscopy on a series of ferromagnetic-semiconductor Ga1-xMnxAs with the Mn content x from ~0.01 to 3.2%. The Fermi level of Ga1-xMnxAs exists in the band gap in the whole x region. The Fermi level is closest to the valence band (VB) at x=1.0% corresponding to the onset of ferromagnetism near the metal-insulator transition (MIT), but it moves away from the VB as x increasing or decreasing from 1.0%. This anomalous behavior of the Fermi level indicates that the ferromagnetism and MIT emerge in the Mn-derived impurity band.Comment: 4 pages, 4 figures, 1 table (minor revision

Valence-band structure of ferromagnetic semiconductor (InGaMn)As

To clarify the whole picture of the valence-band structures of prototype ferromagnetic semiconductors (III,Mn)As (III: In and Ga), we perform systematic experiments of the resonant tunneling spectroscopy on [(In_0.53Ga_0.47)_1-x Mn_x]As (x=0.06-0.15) and In_0.87Mn_0.13As grown on AlAs/ In_0.53Ga_0.47As:Be/ p+InP(001). We show that the valence band of InGaMnAs almost remains unchanged from that of the host semiconductor InGaAs, that the Fermi level exists in the band gap, and that the p-d exchange splitting in the valence band is negligibly small in (InGaMn)As. In the In0.87Mn0.13As sample, although the resonant peaks are very weak due to the large strain induced by the lattice mismatch between InP and InMnAs, our results also indicate that the Fermi level exists in the band gap and that the p-d exchange splitting in the valence band is negligibly small. These results are quite similar to those of GaMnAs obtained by the same method, meaning that there are no holes in the valence band, and that the impurity-band holes dominate the transport and magnetism both in the InGaMnAs and In_0.87Mn_0.13As films. This band picture of (III,Mn)As is remarkably different from that of II-VI-based diluted magnetic semiconductors.Comment: 21 pages, 6 figures, accepted for publication in Phys. Rev.

ANALISIS SWITCHING BARRIERS DAN CUSTOMER SATISFACTION SEBAGAI REKOMENDASI PENINGKATAN ADMISI RAWAT INAP DAN LOYALITAS PASIEN DI RUMAH SAKIT DARMO

Penelitian dilandasi adanya masalah penurunan admisi pasien rawat inap Rumah Sakit Darmo mulai dari tahun 2014 sampai tahun 2016. Tujuan penelitian ini yaitu menyusun rekomendasi peningkatan admisi rawat inap dan loyalitas pasien Rumah Sakit Darmo berdasarkan analisis switching barriers dan customer satisfaction. Jenis penelitian ini adalah observasional yang bersifat analitik dan menggunakan rancang bangun cross sectional. Jumlah sampel dalam penelitian ini adalah 128 pasien. Berdasarkan teknik proportionate stratified random sampling diperoleh sampel kelas I sebanyak 36 pasien, kelas II sebanyak 43 pasien dan kelas III sebanyak 49 pasien. Teknik sampling dalam penelitian ini adalah consecutive sampling yang diambil dengan kriteria inklusi. Secara keseluruhan pasien merasa puas di pelayanan rawat inap. Interpersonal relationship sudah mencapai nilai mean 3,31 menunjukkan bahwa interaksi dokter dan perawat terhadap pasien sangat erat sehingga menjadi hambatan tinggi bagi pasien untuk pindah ke rumah sakit lain. Perceived switching cost dengan nilai mean 2,74 masih merupakan hambatan sedang bagi pasien untuk pindah ke RS lain. Sedangkan, attractiveness of alternatives (daya tarik RS lain) diperoleh nilai mean 1,61, artinya termasuk hambatan tinggi bagi pasien untuk berpindah ke RS lain. Meskipun fasilitas dan kebersihan masih merupakan hambatan sedang bagi pasien RS Darmo. Customer Loyalty masih dinilai cukup dengan mean 2,99 yaitu kesediaan pasien merekomendasikan pelayanan rawat inap dan kesediaan menggunakan kembali layanan RS Darmo. Kesimpulan dari penelitian ini bahwa switching barriers dan customer satisfaction penting dalam meningkatkan admisi rawat inap dan loyalitas pasien dengan cara membuat hambatan yang tinggi agar pasien RS Darmo tidak pindah ke rumah sakit lain. Saran untuk menajemen RS Darmo adalah dapat mengintegrasikan layanan mulai dari pendaftaran online, pembayaran di unit penunjang (laboratorium dan farmasi) ke keuangan untuk mempermudah akses bagi pasien yang rawat inap

Quantum-level control in a III-V-based ferromagnetic-semiconductor heterostructure with a GaMnAs quantum well and double barriers

We investigate the spin-dependent tunneling properties in a three-terminal III-V-based ferromagnetic-semiconductor heterostructure with a 2.5-nm-thick GaMnAs quantum well (QW) and double barriers. We successfully control the quantum levels and modulate the spin-dependent current with varying the voltage of the electrode connected to the GaMnAs QW. Our results will open up a new possibility for realizing three-terminal spin resonant-tunneling devices.Comment: 12 pages, 4 figure

Os efeitos de dieta com suplementação de glutamina sobre a mucosa intestinal do rato desnutrido em crescimento

Glutamine is the most abundant amino acid in the blood and plays a key role in the response of the small intestine to systemic injuries. Mucosal atrophy is an important phenomenon that occurs in some types of clinical injury, such as states of severe undernutrition. Glutamine has been shown to exert powerful trophic effects on the gastrointestinal mucosa after small bowel resection or transplant, radiation injury, surgical trauma, ischemic injury and administration of cytotoxic drugs. Since no study has been performed on the malnourished animal, we examined whether glutamine exerts a trophic effect on the intestinal mucosa of the malnourished growing rat. Thirty-five growing female rats (aged 21 days) were divided into 4 groups: control - chow diet; malnutrition diet; malnutrition+chow diet; and malnutrition+glutamine-enriched chow diet (2%). For the first 15 days of the experiment, animals in the test groups received a malnutrition diet, which was a lactose-enriched diet designed to induce diarrhea and malnutrition. For the next 15 days, these animals received either the lactose-enriched diet, a regular chow diet or a glutamine-enriched chow diet. After 30 days, the animals were weighed, sacrificed, and a section of the jejunum was taken and prepared for histological examination. All the animals had similar weights on day 1 of experiment, and feeding with the lactose-enriched diet promoted a significant decrease in body weight in comparison to the control group. Feeding with both experimental chow-based diets promoted significant body weight gains, although the glutamine-enriched diet was more effective. RESULTS: The morphological and morphometric analyses demonstrated that small intestinal villous height was significantly decreased in the malnourished group, and this change was partially corrected by the two types of chow-based diet. Crypt depth was significantly increased by malnutrition, and this parameter was partially corrected by the two types of chow-based diet. The glutamine-enriched diet resulted in the greatest reduction of crypt depth, and this reduction was also statistically significant when compared with control animals. CONCLUSIONS: Enteral glutamine has some positive effects on body weight gain and trophism of the jejunal mucosa in the malnourished growing rat.A glutamina é o aminoácido mais abundante no sangue e exerce papel importante na resposta do intestino delgado às agressões sistêmicas. Atrofia da mucosa intestinal ocorre em algumas afecções clínicas como desnutrição grave. Foi demonstrado que a glutamina tem ação trófica em situações como período pós-operatório de ressecção ou transplante intestinal, radioterapia, trauma cirúrgico, isquemia intestinal ou administração de drogas citotóxicas. Tais estudos não foram realizados em animais desnutridos em fase de crescimento. Desta forma, no presente trabalho verificamos se a glutamina exerce ação trófica sobre a mucosa intestinal do rato desnutrido em fase de crescimento. Foram utilizadas 35 ratas com 21 dias de idade, e divididas em 4 grupos: controle - dieta normal; desnutrição - provocada por diarréia induzida pela administração de dieta rica em lactose durante 15 dias; desnutrição+dieta normal durante os 15 dias subseqüentes; desnutrição + dieta rica em glutamina (2%). Após 30 dias de experimento os animais foram pesados, mortos e um segmento de jejuno foi colhido para estudos histológicos e histomorfométricos. Os grupos de animais apresentaram médias de pesos semelhantes no primeiro dia de estudo, sendo que a alimentação com dieta rica em lactose (grupo desnutrido) provocou significativa queda de peso em relação aos controles. A re-alimentação com ambos os tipos de dieta promoveu ganho significativo de peso corpóreo, embora a dieta rica em glutamina tenha sido mais eficaz. Os estudos histológicos e histomorfométricos demonstraram que a desnutrição provocou significativa redução do comprimento das vilosidades e aumento das criptas, sendo estas alterações parcialmente corrigidas por ambos os tipos de dieta. A redução no comprimento das criptas foi mais significativa no grupo com glutamina. Conclui-se que a administração enteral de glutamina tem efeitos positivos sobre o ganho ponderal e sobre o trofismo da mucosa intestinal em animais desnutridos em fase de crescimento

GaMnAs-based magnetic tunnel junctions with an AlMnAs barrier

We investigate the spin-dependent transport of GaMnAs-based magnetic tunnel junctions (MTJs) containing a paramagnetic AlMnAs barrier with various thicknesses. The barrier height of AlMnAs with respect to the Fermi level of GaMnAs is estimated to be 110 meV. We observe tunneling magnetoresistance (TMR) ratios up to 175% (at 2.6 K), which is higher than those of the GaMnAs-based MTJs with other barrier materials in the same temperature region. These high TMR ratios can be mainly attributed to the relatively high crystal quality of AlMnAs and the suppression of the tunneling probability near at the in-plane wave-vector k||=0.Comment: 12 pages, 3 figures, accepted for publication in Appl. Phys. Let